Fourier transform infrared and differential scanning calorimetric studies of a surface-active material from rabbit lung.

A surface-active material with a chemical composition consistent with lung surfactant and with the ability to lower surface tension on a Wilhelmy balance to about 6 mN/m, has been isolated from rabbit pulmonary lavage. The thermotropic properties have been characterized with the techniques of Fourier transform infrared spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC). FT-IR melting curves were constructed from the temperature-dependence of the lipid CH2 symmetric stretching vibrational frequencies near 2850 cm-1. A broad gel-liquid crystal phase transition with an onset temperature of about 22 degrees C, and a completion temperature of about 38 degrees C was observed, with slight sample-to-sample variations in temperatures. A similar completion temperature was noted in DSC endotherms. Ca2+ (5-10 mM) increased the onset temperature of the lipid-melting event, and induced an ordering of surfactant and of its lipid extract at all temperatures studied. The effect on the lipids was suggestive of a Ca2+-induced phase separation caused by ion binding to phosphatidylglycerol and other acidic components. Evidence for a direct interaction between Ca2+ and the phosphate groups was suggested through small Ca2+-induced shifts in the 1090 cm-1 symmetric PO2 stretching frequency. Removal of most of the protein component from a 10:1 (lipid/protein, w/w) sample caused an ordering of the resultant lipid fractions. In contrast, removal of most of the protein component from a 20:1 sample resulted in no change in lipid order or thermotropic behavior. These observations are discussed in light of the roles played both by Ca2+ and protein in the spreading of surfactant. The power of FT-IR to acquire useful structural information from complex biological tissues is demonstrated.

Hydrogen exchange dynamics of the P22 virion determined by time-resolved Raman spectroscopy. Effects of chromosome packaging on the kinetics of nucleotide exchanges.

We describe the application of laser Raman spectroscopy to probe hydrogen isotope exchange dynamics of nucleic acid and protein constituents in a double-stranded DNA virus, the icosahedral bacteriophage P22. The Raman dynamic method employs a dialysis flow cell to control D2O efflux into an H2O solution of the virus sample while the rates of deuterium exchange of protons in the viral nucleic acid and protein molecules are measured spectrophotometrically in real time. The method provides structural and kinetic information about three different and distinct classes of exchangeable protons of the native virion: (1) labile imino (NH) and amino (NH2) protons of the bases which participate in Watson-Crick hydrogen bonding in the packaged genome; (2) pseudolabile purinic (8CH) protons that line the major groove of packaged P22 DNA; and (3) main-chain amide (NH) protons of viral subunits comprising the shell that encapsidates the DNA. The results obtained on P22 demonstrate that interchange of aqueous solvent with the virion interior is rapid and complete. We find that while labile protons of packaged DNA exchange rapidly, most amide protons in capsid subunits are resistant to solvent-catalyzed exchange. Further, stereospecific retardation of exchange is observed for major-groove protons of the packaged P22 genome. The quantitative measurements can be summarized and interpreted as follows. (1) Imino and amino protons of all bases in packaged P22 DNA exchange more rapidly (approximately 2-fold faster) than the corresponding protons in unpackaged P22 DNA. Remarkably, packaging actually accelerates labile imino and amino hydrogen exchanges of the viral DNA, an effect which can be attributed to selective stabilization in the packaged chromosome of a base-pair open state (breathing model). (2) Conversely, purine 8CH exchange rates in packaged P22 DNA are significantly retarded in comparison to those of unpackaged P22 DNA. The observed 8CH exchange retardation effects are similar for both adenine and guanine residues, indicating that they do not originate from purine-specific interactions but probably reflect steric shielding of the major groove of packaged DNA from free access to solvent. This effect is likely distributed throughout the 43,400 base-pair genome. (3) Only a small population (approximately 15 to 20%) of subunit amide protons exchanges within the time frame of complete exchange of all protons of packaged P22 DNA. Complete exchange of the capsid is not achieved even after several months of incubation at 40 degrees C.(ABSTRACT TRUNCATED AT 400 WORDS)

How to write a case report.

BACKGROUND: Since before Hippocrates, case reports have provided a rich resource for teaching and research in medicine. Case reports are published by many prominent journals--more than 140,000 case reports are indexed in MEDLINE from 1996 to present--and a number of narrative guidelines for the preparation of case reports have appeared in the medical literature. To facilitate the preparation of case reports, we reviewed the existing guidelines and a random sampling of published case reports and created a fill-in-the-blanks worksheet for physicians to use to capture unique scientific observations. Although originally developed to assist family practice residents to write case reports, the case report worksheet can be used by physicians in any practice setting and any discipline to collect and report interesting, unusual, or newsworthy cases.

Teaching family-centered perinatal care in family medicine, Part 2.

Pregnancy, childbirth, postpartum, and infant care are a continuum in the family life cycle for which the family physician is especially qualified to provide primary, comprehensive care. The purpose of this paper is to document and share the controversies, wisdom, and knowledge about caring for women and their families before, during, and after pregnancy. Family physicians can be leaders in developing an appropriate perinatal care system for the community. The level of care the family physician chooses to provide is discretionary. However, the family physician should be invested in ensuring that all families receive the greatest benefit from pregnancy, birth, and the newborn experience. Interest in perinatal care in family medicine is increasing, as reflected by the growing numbers participating in the Society of Teachers of Family Medicine Working Group on Family-Centered Perinatal Care. The authors of this article, who are active in this working group, hope that this information is useful in designing a balanced curriculum and delivery system for perinatal care in family medicine training programs.

Teaching family-centered perinatal care in family medicine, Part I.

Pregnancy, childbirth, postpartum, and infant care are a continuum in the family life cycle for which the family physician is especially qualified to provide primary, comprehensive care. The purpose of this paper is to document and share the controversies, wisdom, and knowledge about caring for women and their families before, during, and after pregnancy. Family physicians can be leaders in developing an appropriate perinatal care system for the community. The level of care the family physician chooses to provide is discretionary. However, the family physician should be invested in ensuring that all families receive the greatest benefit from pregnancy, birth, and the newborn experience. Interest in perinatal care in family medicine is increasing, as reflected by the growing numbers participating in the Society of Teachers of Family Medicine Working Group on Family-Centered Perinatal Care. The authors of this article, who are active in this working group, hope that this information is useful in designing a balanced curriculum and delivery system for perinatal care in family medicine training programs.

Screening for microalbuminuria to prevent nephropathy in patients with diabetes: a systematic review of the evidence.

OBJECTIVE: Our goal was to evaluate whether screening patients with diabetes for microalbuminuria (MA) is effective according to the criteria developed by Frame and Carlson and those of the US Preventive Services Task Force. STUDY DESIGN: We searched the MEDLINE database (1966-present) and bibliographies of relevant articles. OUTCOMES MEASURED: We evaluated the impact of MA screening using published criteria for periodic health screening tests. The effect of the correlation between repeated tests on the accuracy of a currently recommended testing strategy was analyzed. RESULTS: Quantitative tests have reported sensitivities from 56% to 100% and specificities from 81% to 98%. Semiquantitative tests for MA have reported sensitivities from 51% to 100% and specificities from 21% to 100%. First morning, morning, or random urine sampling appear feasible. Assuming an individual test sensitivity of 90%, a specificity of 90%, and a 10% prevalence of MA, the correlation between tests would have to be lower than 0.1 to achieve a positive predictive value for repeated testing of 75%. CONCLUSIONS: Screening for MA meets only 4 of 6 Frame and Carlson criteria for evaluating screening tests. The recommended strategies to overcome diagnostic uncertainty by using repeated testing are based on expert opinion, are difficult to follow in primary care settings, do not improve diagnostic accuracy sufficiently, and have not been tested in a controlled trial. Although not advocated by the American Diabetes Association, semiquantitative MA screening tests using random urine sampling have acceptable accuracy but may not be reliable in all settings.

Induction of labor.

Labor is induced if pregnancy must be completed before the onset of spontaneous labor, usually for reasons of maternal illness, fetal distress or, most commonly, prolonged pregnancy. Although various mechanical methods are available for labor induction, pharmacologic methods are more commonly used. Oxytocin is the standard treatment. Prostaglandin E2 may be useful when the cervix is not favorable for induction. This article reviews both nonpharmacologic and pharmacologic methods for labor induction, and offers suggestions for successful induction in various circumstances.

Glucose-6-phosphate dehydrogenase from Saccharomyces cerevisiae is a glycoprotein.

A commercial preparation of glucose-6-phosphate dehydrogenase (G6PD) purified from Saccharomyces cerevisiae was subjected to PAGE analysis under both nondenaturing and denaturing conditions. The enzyme, identified by both activity staining and anti-yeast G6PD antibody immunoblotting, was shown to contain carbohydrate using the highly specific periodate-digoxigenin antidigoxigenin method which is diagnostic for glycoproteins.

Deuterium exchange of operator 8CH groups as a Raman probe of repressor recognition: interactions of wild-type and mutant lambda repressors with operator OL1.

The rate of deuterium exchange of a purine 8CH group in DNA is highly sensitive to both macromolecular secondary structure and intermolecular interactions which restrict solvent access to the major groove [Lamba, O.P., Becka, R., & Thomas, G.J., Jr. (1990) Biopolymers 29, 1465-1477]. We have exploited the sensitivity of the 8CH----8CD reaction to probe DNA recognition by the helix-turn-helix (HTH) motif of phage lambda cI repressor. We find that purine exchanges in the 19-base-pair OL1 operator are strongly and specifically restricted by binding of the HTH N-terminal domain of the repressor fragment (RF) comprising residues 1-102. The kinetics indicate large-scale obstruction of solvent access to operator 7N-8C purine sites. Interpretation of the exchange kinetics using a simple model suggests that only 7 purine residues (5 of 10 adenines and 2 of 9 guanines) remain unrestricted with respect to 8CH exchange in complexes of OL1 with the wild-type repressor. On the other hand, the 8CH exchange profile for the complex of OL1 with the Tyr88----Cys mutant repressor indicates that 9 purines (7 adenines and 2 guanines) are exchangeable. These results suggest important differences in major groove recognition in the two complexes. The proposed 8CH labeling profiles are consistent with molecular models of related complexes determined by X-ray crystallography [Jordan, S.R., & Pabo, C.O. (1988) Science 242, 893-899] and indicate that the structures observed in the crystal are largely maintained in solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Fourier-transform infrared spectroscopy studies of lipid/protein interaction in pulmonary surfactant.

The thermotropic behavior of intact bovine lung surfactant and its hydrophobic extract has been monitored via the temperature dependence of the 2850 cm-1 phospholipid acyl chain CH2 symmetric stretching frequencies in the IR spectrum. A broad, reversible, melting event was noted from about 15 to 40 degrees C in both the lipid extract and the native surfactant. Slight protein-induced disordering of the lipid acyl chains was evident. The melting event was confirmed by differential scanning calorimetry. The major surfactant protein, a 30-36-kDa class of glycoprotein (SP-A), has been isolated from bovine lung lavage and purified by affinity chromatography. SP-A was reconstituted into a binary lipid mixture of acyl chain perdeuterated dipalmitoylphosphatidylcholine/dipalmitoylphosphatidylglycerol (DPPC-d62/DPPG, 85:15 w/w), a ratio which approximates that in surfactant. Use of DPPC-d62 permitted the FT-IR determination of the effect of protein on the thermotropic behavior of individual phospholipids in the binary mixture. High levels of SP-A induced an ordering of the phospholipids, as shown by an increase in the transition temperature of DPPC-d62 compared to the lipid model. In contrast, a mixture of the other surfactant proteins induced a progressive disordering of the phospholipids and disruption of the cooperativity of the melting event. Transition widths of about 3 degrees, 9 degrees, and 27 degrees were noted for protein:lipid ratios of 0, 1:1, and 2:1 (w/w), respectively. Possible roles for the various proteins in surfactant function are discussed in light of these data.

Recurrent giant cell tumors of the tendon sheath.

Seventy patients underwent surgical excision of a giant cell tumor of the tendon sheath. The patients were monitored for an average of 3 years 4 months. Nineteen of the 70 patients (27%) had a surgically and histologically documented recurrence at an average of 2 years 3 months (range, 3 months to 10 years) following the initial procedure. Eight of 19 patients (42%) with recurrence had a prior recurrence. Statistically significant risk factors for recurrence included presence of adjacent degenerative joint disease, location at the distal interphalangeal joint of the finger or interphalangeal joint of the thumb, and radiographic presence of an osseous pressure erosion. Age, gender, size, and location within the digit (volar vs. dorsal) were not risk factors for recurrence. Awareness of these associations should be reflected in the surgeon's approach and preoperative discussion with the patient.

Osteomyelitis of the tubular bones of the hand.

The records of 700 patients with hand infections were reviewed. Forty-six (6%) had osteomyelitis of the metacarpals or phalangeal bones. The cause was post-traumatic in 57%, postoperative in 15%, hematogenous in 13%, spread from contiguous infections in 9%, and unidentified in 6%. Twenty-two percent of the patients had vascular insufficiency and/or were immunocompromised. History, physical exam, plain x-rays, and open biopsy and culture were most helpful in establishing the diagnosis. Laboratory studies and bone scans were less helpful. Cultures were positive in 74% of patients, with a noteworthy number of mixed infections (35%) and gram-positive infections (35%). Gram-negative infections accounted for 15%, fungal infections for 12%, and mycobacterial infections for 3%. Surgical management varied from simple curettage to more elaborate staged reconstructions and/or arthrodeses. Despite provision of aggressive surgical care and use of appropriate antibiotics, the overall amputation rate was 39% (18/46). A delay of more than 6 months from onset of symptoms to diagnosis and definitive treatment led to amputation in 6 of 7 patients (86%), 2 of whom had squamous-cell carcinoma. Of the 12 patients who underwent more than 3 surgical procedures, 8 ultimately underwent amputation and 2 had marked disability.

Infrared spectroscopic investigations of pulmonary surfactant. Surface film transitions at the air-water interface and bulk phase thermotropism.

The molecular structure of the phospholipid component of intact pulmonary surfactant isolated from bovine lung lavage has been examined by Fourier transform infrared spectroscopy. Two different physical states of the surfactant were examined by means of different infrared spectroscopic sampling techniques. Transmission infrared experiments were used to study the surfactant in the bulk phase. In these experiments, the thermotropic behavior of the bulk surfactant was monitored by temperature-induced variations in the phospholipid acyl chain CH2 stretching frequencies. A broad phase transition (confirmed by differential scanning calorimetry) was noted with an onset temperature near 15 degrees C and a completion temperature near 42 degrees C. In addition to the bulk transmission experiments, external reflection infrared spectroscopy was used to examine surfactant films in situ at the air-water interface. As surface pressure was increased from 0 to 43 dyn/cm, a gradual and continuous decrease in the CH2 stretching frequency was noted for the surfactant. Thus, under surface pressures which correspond to large lung volumes in vivo, the surfactant acyl chains exist mostly in the ordered (trans) configuration. The frequency shift in the CH2 stretching mode is consistent with a continuous ordering of the acyl chains upon compression over the pressure range 0-43 dyn/cm, and implies that a weakly cooperative phase transition occurs in the hydrocarbon region of the surface film. The surface film transition is especially noted in the pressure-area curve of the surfactant and approximates in two dimensions the broad thermotropic phase transition of the bulk phase surfactant. Substantial differences were observed between the response to surface pressure changes of intact surfactant compared with the main surfactant phospholipid, 1,2-dipalmitoyl-sn--glycero-3-phosphocholine. The changes in response are attributed to the presence of additional surfactant components. The current work demonstrates the ability of infrared spectroscopy to obtain structural information on the surfactant in physical states that directly relate to those in vivo.

Conformation and interactions of the packaged double-stranded DNA genome of bacteriophage T7.

The structure of the packaged double-stranded DNA genome of bacteriophage T7 was compared to that of unpackaged T7 DNA using digital difference Raman spectroscopy. Spectral data were obtained at 25 degrees C from native T7 virus (100 mg/mL), empty T7 capsids (50 mg/mL), and purified T7 DNA (40 mg/mL) in buffer containing 200 mM NaCl, 10 mM MgCl2, and 10 mM Tris at pH 7.5. At these conditions, the local conformation of T7 DNA was not affected by packaging. Specifically, the local B-form secondary structure of unpackaged T7 DNA, including furanose C2'-endo pucker, anti glycosyl torsion, Watson-Crick base pairing, and base stacking, were essentially fully (> 98%) retained when the genome was condensed within the viral capsid. However, the average electrostatic environment of T7 DNA phosphates was altered dramatically by packaging as revealed by large perturbations in the Raman bands associated with localized vibrations of the DNA phosphate groups. The change in the phosphate environment was attributed to Mg2+ ions that were packaged with the genomic DNA, and the observed Raman perturbations of genomic DNA were equivalent to those generated by a 50-100-fold increase in Mg2+ concentration in aqueous phosphodiester model compounds. The T7 data were qualitatively and quantitatively similar to those observed previously for packaged DNA of bacteriophage P22 and imply that genomic DNAs of T7 and P22 are both organized in a similar fashion within their respective capsids. The results show that the condensed genome does not contain kinks or folds that would disrupt the local B conformation by more than 2%. The present findings are discussed in relation to previously proposed models for condensation and organization of double-stranded and single-stranded viral DNA.