Improving image quality of sparse-view lung tumor CT images with U-Net

BACKGROUND

We aimed to improve the image quality (IQ) of sparse-view computed tomography (CT) images using a U-Net for lung metastasis detection and determine the best tradeoff between number of views, IQ, and diagnostic confidence.

METHODS

CT images from 41 subjects aged 62.8 ± 10.6 years (mean ± standard deviation, 23 men), 34 with lung metastasis, 7 healthy, were retrospectively selected (2016-2018) and forward projected onto 2,048-view sinograms. Six corresponding sparse-view CT data subsets at varying levels of undersampling were reconstructed from sinograms using filtered backprojection with 16, 32, 64, 128, 256, and 512 views. A dual-frame U-Net was trained and evaluated for each subsampling level on 8,658 images from 22 diseased subjects. A representative image per scan was selected from 19 subjects (12 diseased, 7 healthy) for a single-blinded multireader study. These slices, for all levels of subsampling, with and without U-Net postprocessing, were presented to three readers. IQ and diagnostic confidence were ranked using predefined scales. Subjective nodule segmentation was evaluated using sensitivity and Dice similarity coefficient (DSC); clustered Wilcoxon signed-rank test was used.

RESULTS

The 64-projection sparse-view images resulted in 0.89 sensitivity and 0.81 DSC, while their counterparts, postprocessed with the U-Net, had improved metrics (0.94 sensitivity and 0.85 DSC) (p = 0.400). Fewer views led to insufficient IQ for diagnosis. For increased views, no substantial discrepancies were noted between sparse-view and postprocessed images.

CONCLUSIONS

Projection views can be reduced from 2,048 to 64 while maintaining IQ and the confidence of the radiologists on a satisfactory level.

RELEVANCE STATEMENT

Our reader study demonstrates the benefit of U-Net postprocessing for regular CT screenings of patients with lung metastasis to increase the IQ and diagnostic confidence while reducing the dose.

KEY POINTS

• Sparse-projection-view streak artifacts reduce the quality and usability of sparse-view CT images. • U-Net-based postprocessing removes sparse-view artifacts while maintaining diagnostically accurate IQ. • Postprocessed sparse-view CTs drastically increase radiologists' confidence in diagnosing lung metastasis.

Differential recognition of lipid domains by two Gb3-binding lectins

The two lectins LecA from Pseudomonas aeruginosa and the B-subunit of Shiga toxin from Shigella dysenteriae (StxB) share the glycosphingolipid globotriaosylceramide (Gb3) as receptor. Counterintuitively, we found that LecA and StxB segregated into different domains after recognizing Gb3 at the plasma membrane of cells. We hypothesized that the orientation of the carbohydrate head group of Gb3 embedded in the lipid bilayer differentially influences LecA and StxB binding. To test this hypothesis, we reconstituted lectin-Gb3 interaction using giant unilamellar vesicles and were indeed able to rebuild LecA and StxB segregation. Both, the Gb3 fatty acyl chain structure and the local membrane environment, modulated Gb3 recognition by LecA and StxB. Specifically, StxB preferred more ordered membranes compared to LecA. Based on our findings, we propose comparing staining patterns of LecA and StxB as an alternative method to assess membrane order in cells. To verify this approach, we re-established that the apical plasma membrane of epithelial cells is more ordered than the basolateral plasma membrane. Additionally, we found that StxB recognized Gb3 at the primary cilium and the periciliary membrane, whereas LecA only bound periciliary Gb3. This suggests that the ciliary membrane is of higher order than the surrounding periciliary membrane.

Shiga toxin binding alters lipid packing and the domain structure of Gb3-containing membranes: a solid-state NMR study

We studied the influence of globotriaosylceramide (Gb3) lipid molecules on the properties of phospholipid membranes composed of a liquid ordered (lo)/liquid disordered (ld) phase separated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/N-palmitoyl-d-erythro-sphingosylphosphorylcholine (PSM)/cholesterol mixture (40/35/20, mol/mol/mol) supplemented with 5 mol% of either short acyl chain palmitoyl-Gb3 or long acyl chain lignoceryl-Gb3 using 2H solid-state NMR spectroscopy. To this end, both globotriaosylceramides were chemically synthesized featuring a perdeuterated lipid acyl chain. The solid-state 2H NMR spectra support the phase separation into a POPC-rich ld phase and a PSM/cholesterol-rich lo phase. The long chain lignoceryl-Gb3 showed a rather unusual order parameter profile of the acyl chain, which flattens out for the last ∼6 methylene segments. Such an odd chain conformation can be explained by partial chain interdigitation and/or a very fluid midplane region of the membrane. Possibly, the Gb3 molecules may thus preferentially be localized at the lo/ld phase boundary. In contrast, the short chain palmitoyl-Gb3 was well associated with the PSM/cholesterol-rich lo phase. Gb3 molecules act as membrane receptors for the Shiga toxin (STx) produced by Shigella dysenteriae and by enterohemorrhagic strains of Escherichia coli (EHEC). The B-subunits of STx (STxB) forming a pentameric structure were produced recombinantly and incubated with the membrane mixtures leading to alterations in the lipid packing properties and lateral organization of the membranes. Typically, STxB binding led to a decrease in lipid chain order in agreement with partial immersion of protein segments into the lipid-water interface of the membrane. In the presence of STxB, Gb3 preferentially partitioned into the lo membrane phase. In particular the short acyl chain palmitoyl-Gb3 showed very similar chain order parameters to PSM. In the presence of STxB, all lipid species showed isotropic contributions to the 2H NMR powder spectra; this was most pronounced for the Gb3 molecules. Such isotropic contributions are caused by highly curved membrane structures, which have previously been detected as membrane invaginations in fluorescence microscopy. Our analysis estimated that STxB induced highly curved membrane structures with a curvature radius of less than ∼10 nm likely related to the insertion of STxB segments into the lipid-water interface of the membrane.

A self-assembled, modular nucleic acid-based nanoscaffold for multivalent theranostic medicine

Rationale: Within the field of personalized medicine there is an increasing focus on designing flexible, multifunctional drug delivery systems that combine high efficacy with minimal side effects, by tailoring treatment to the individual.

Methods: We synthesized a chemically stabilized ~4 nm nucleic acid nanoscaffold, and characterized its assembly, stability and functional properties in vitro and in vivo. We tested its flexibility towards multifunctionalization by conjugating various biomolecules to the four modules of the system. The pharmacokinetics, targeting capability and bioimaging properties of the structure were investigated in mice. The role of avidity in targeted liver cell internalization was investigated by flow cytometry, confocal microscopy and in vivo by fluorescent scanning of the blood and organs of the animals.

Results: We have developed a nanoscaffold that rapidly and with high efficiency can self-assemble four chemically conjugated functionalities into a stable, in vivo-applicable system with complete control of stoichiometry and site specificity. The circulation time of the nanoscaffold could be tuned by functionalization with various numbers of polyethylene glycol polymers or with albumin-binding fatty acids. Highly effective hepatocyte-specific internalization was achieved with increasing valencies of tri-antennary galactosamine (triGalNAc) in vitro and in vivo.

Conclusion: With its facile functionalization, stoichiometric control, small size and high serum- and thermostability, the nanoscaffold presented here constitutes a novel and flexible platform technology for theranostics.

Synthesis and Excellent Duplex Stability of Oligonucleotides Containing 2'-Amino-LNA Functionalized with Galactose Units

A convenient method for the preparation of oligonucleotides containing internally-attached galactose and triantennary galactose units has been developed based on click chemistry between 2′-N-alkyne 2′-amino-LNA nucleosides and azido-functionalized galactosyl building blocks. The synthesized oligonucleotides show excellent binding affinity and selectivity towards complementary DNA/RNA strands with an increase in the melting temperature of up to +23.5 °C for triply-modified variants.

Synthesis and Biophysical Investigations of Oligonucleotides Containing Galactose-Modified DNA, LNA, and 2'-Amino-LNA Monomers

Galactose-modified thymidine, LNA-T, and 2'-amino-LNA-T nucleosides were synthesized, converted into the corresponding phosphoramidite derivatives and introduced into short oligonucleotides. Compared to the unmodified control strands, the galactose-modified oligonucleotides in general, and the N2'-functionalized 2'-amino-LNA derivatives in particular, showed improved duplex thermal stability against DNA and RNA complements and increased ability to discriminate mismatches. In addition, the 2'-amino-LNA-T derivatives induced remarkable 3'-exonuclease resistance. These results were further investigated using molecular modeling studies.

2-Hydroxy Fatty Acid Enantiomers of Gb3 Impact Shiga Toxin Binding and Membrane Organization

Shiga toxin subunit B (STxB) binding to its cellular receptor Gb3 leads to the formation of protein-lipid clusters and bending of the membrane. A newly developed synthetic route allowed synthesizing the biologically most relevant Gb3-C24:1 2OH species with both, the natural (Gb3-R) as well as the unnatural (Gb3-S) configuration of the 2OH group. The derivatives bind STxB with identical nanomolar affinity, while the propensity to induce membrane tubules in giant unilamellar vesicles is more pronounced for Gb3-S. Fluorescence and atomic force microscopy images of phase-separated supported membranes revealed differences in the lateral organization of the protein on the membrane. Gb3-R favorably induces large and tightly packed protein clusters, while a lower protein density is found on Gb3-S doped membranes.

Impact of Structural Differences in Galactocerebrosides on the Behavior of 2D Monolayers

The molecular interactions of three biologically important galactocerebrosides have been studied in monolayers formed at the soft air/water interface as 2D model membranes. Highly surface-sensitive techniques as GIXD (grazing incidence X-ray diffraction), IRRAS (infrared reflection-absorption spectroscopy), and BAM (Brewster angle microscopy) have been used. The study reveals that small differences in the chemical structure have a relevant impact on the physical-chemical properties and intermolecular interactions. The presence of a 2-d-hydroxyl group in the fatty acid favored for GalCer C24:0 (2-OH) monolayers a higher hydration state of the headgroup at low lateral pressures (<25 mN/m) and a higher condensation effect above 30 mN/m. An opposite behavior was recorded for GalCer C24:0 and GalCer C24:1, for which the intermolecular interactions are defined by the weakly hydrated but strong H-bonded interconnected head groups. Additionally, the 15-cis-double bond in the fatty acid chain (nervonic acid) of GalCer C24:1 stabilized the LE phase but did not disturb the packing parameters of the LC phase as compared with the saturated compound GalCer C24:0.

Influence of length and conformation of saccharide head groups on the mechanics of glycolipid membranes: Unraveled by off-specular neutron scattering

The mechanical properties of multilayer stacks of Gb3 glycolipid that play key roles in metabolic disorders (Fabry disease) were determined quantitatively by using specular and off-specular neutron scattering. Because of the geometry of membrane stacks deposited on planar substrates, the scattered intensity profile was analyzed in a 2D reciprocal space map as a function of in-plane and out-of-plane scattering vector components. The two principal mechanical parameters of the membranes, namely, bending rigidity and compression modulus, can be quantified by full calculation of scattering functions with the aid of an effective cut-off radius that takes the finite sample size into consideration. The bulkier "bent" Gb3 trisaccharide group makes the membrane mechanics distinctly different from cylindrical disaccharide (lactose) head groups and shorter "bent" disaccharide (gentiobiose) head groups. The mechanical characterization of membranes enriched with complex glycolipids has high importance in understanding the mechanisms of diseases such as sphingolipidoses caused by the accumulation of non-degenerated glycosphingolipids in lysosomes or inhibition of protein synthesis triggered by the specific binding of Shiga toxin to Gb3.

The minimal important difference of exercise tests in severe COPD

Our aim was to determine the minimal important difference (MID) for 6-min walk distance (6MWD) and maximal cycle exercise capacity (MCEC) in patients with severe chronic obstructive pulmonary disease (COPD). 1,218 patients enrolled in the National Emphysema Treatment Trial completed exercise tests before and after 4-6 weeks of pre-trial rehabilitation, and 6 months after randomisation to surgery or medical care. The St George's Respiratory Questionnaire (domain and total scores) and University of California San Diego Shortness of Breath Questionnaire (total score) served as anchors for anchor-based MID estimates. In order to calculate distribution-based estimates, we used the standard error of measurement, Cohen's effect size and the empirical rule effect size. Anchor-based estimates for the 6MWD were 18.9 m (95% CI 18.1-20.1 m), 24.2 m (95% CI 23.4-25.4 m), 24.6 m (95% CI 23.4-25.7 m) and 26.4 m (95% CI 25.4-27.4 m), which were similar to distribution-based MID estimates of 25.7, 26.8 and 30.6 m. For MCEC, anchor-based estimates for the MID were 2.2 W (95% CI 2.0-2.4 W), 3.2 W (95% CI 3.0-3.4 W), 3.2 W (95% CI 3.0-3.4 W) and 3.3 W (95% CI 3.0-3.5 W), while distribution-based estimates were 5.3 and 5.5 W. We suggest a MID of 26 ± 2 m for 6MWD and 4 ± 1 W for MCEC for patients with severe COPD.

Recombinant domains of mouse nidogen-1 and their binding to basement membrane proteins and monoclonal antibodies

The basement membrane protein, nidogen-1, was previously shown to consist of three globular domains, G1 to G3, and two connecting segments. Nidogen-1 is a major mediator in the formation of ternary complexes with laminins, collagen IV, perlecan and fibulins. In the present study, we have produced recombinant proteins of these predicted domains in mammalian cells and used these proteins for crystallographic and binding epitope analyses. These fragments included G1, G2, the rod domain and a slightly larger G3 structure; all were obtained in good yields and were shown to be properly folded using electron microscopy. Surface plasmon resonance assays demonstrated high affinity binding (Kd = 3-9 nM) of domain G2 for collagen IV, perlecan domain IV-1 and fibulin-2, and a more moderate Kd for fibulin-1C. Domain G3 contained high affinity binding sites for the laminin gamma1 chain and collagen IV (Kd = 1 nM) and weaker binding sites for fibulin-1C and fibulin-2. A moderate binding affinity was also observed between domain G1 and fibulin-2, while no activity could be detected for the nidogen rod domain. Together, these data indicate the potential of nidogen-1 for multiple interactions within basement membranes. A similar binding repertoire was also identified for seven rat monoclonal antibodies that bound with Kd = 2-30 nM to either G1, G1-G2, G2, the rod domain or G3. Three of the antibodies showed strongly reduced binding to G2 and G3 after complex formation with either a perlecan domain or laminin-1.

Crystal structure and mutational analysis of a perlecan-binding fragment of nidogen-1

Nidogen, an invariant component of basement membranes, is a multifunctional protein that interacts with most other major basement membrane proteins. Here, we report the crystal structure of the mouse nidogen-1 G2 fragment, which contains binding sites for collagen IV and perlecan. The structure is composed of an EGF-like domain and an 11-stranded beta-barrel with a central helix. The beta-barrel domain has unexpected similarity to green fluorescent protein. A large surface patch on the beta-barrel is strikingly conserved in all metazoan nidogens. Site-directed mutagenesis demonstrates that the conserved residues are involved in perlecan binding.

Use of the endometrial pipelle in the diagnosis of early abnormal gestations

OBJECTIVE

To determine the sensitivity and specificity of the endometrial pipelle (Unimar, Wilton, CT) in detecting intrauterine chorionic villi, as compared to standard suction dilation and curettage (D and C).

DESIGN

Prospective clinical study.

SETTING

U. S. Navy Hospital near Tokyo, Japan. Small community hospital.

PATIENT(S)

All patients presenting for the surgical management of an early abnormal gestation were enrolled prospectively. The patient's age, gravidy, parity, estimated gestational age (EGA), diagnosis, preoperative beta human chorionic gonadotropin (betahCG) level, and preoperative transvaginal ultrasound (TVUS) data were recorded.

INTERVENTION(S)

An endometrial biopsy was performed in the operating room prior to standard suction dilatation and curettage (D and C).

MAIN OUTCOME MEASURE(S)

The presence of chorionic villi in the endometrial biopsy and curettage specimens were recorded for each patient.

RESULT(S)

The sensitivity of the endometrial pipelle in detecting intrauterine chorionic villi was 63% and the specificity was 80%.

CONCLUSION(S)

In the diagnosis of an early abnormal gestation, particularly in excluding an ectopic pregnancy, it would be ideal to replace the more invasive D and C with the outpatient endometrial biopsy in detecting intrauterine chorionic villi. However, the limited sensitivity of the endometrial biopsy limits its application in this clinical scenario. Our results compare with two previous studies and add to the limited patient database on this topic.

Laboratory testing for preeclampsia: result trends and screening recommendations

To better direct screening for preeclampsia, we describe the result trends of the laboratory tests used in the workup of preeclampsia at our institution. The clinical characteristics of patients with abnormal test results are further detailed. The objective of the study is to recommend a laboratory screening regimen for preeclampsia based on the data. All patients who delivered at National Naval Medical Center from February to July 1996 who had blood urea nitrogen, creatinine, aspartate aminotransferase, alanine aminotransferase, or uric acid determinations as part of a workup for preeclampsia were identified. Results are reported, and the clinical characteristics of patients with abnormal tests were obtained from the medical record. Abnormalities of uric acid and liver enzymes were few in our patient population (6% and 7%, respectively). The majority of patients with abnormal uric acid and liver function tests had the classic clinical symptoms of preeclampsia; therefore, the laboratory data added little to the clinical diagnosis. There was a high rate of renal test abnormalities, necessitating further investigation. We recommend omitting liver function and uric acid testing in the routine screening for preeclampsia. The high incidence of abnormal renal tests warrants continued use of this screening test and, more importantly, further investigation into the relationship between abnormal renal tests and disease course.

Characterizing "blue blobs". Immunohistochemical staining and ultrastructural study

OBJECTIVE

To investigate the nature and origin of "blue blobs" (Bbs) in atrophic Pap smears in postmenopausal women and to study their clinical significance.

STUDY DESIGN

A retrospective study of 412 atrophic Pap smears from postmenopausal women was done to detect the presence of Bbs. The smears from 24 cases showing Bbs were further studied to evaluate the nature of the Bbs with special stains, immunohistochemistry and electron microscopy.

RESULTS

Bbs showed a heterogeneous morphology, with variable numbers and staining intensity. The diameter of Bbs was approximately equivalent to that of a parabasal/intermediate squamous cell. Special stains showed Bbs to be positive for periodic acid-Schiff and methyl green pyronin and negative for mucicarmine and calcium. Immunohistochemistry revealed Bbs to be positive for cytokeratin, epithelial membrane antigen and carcinoembryonic antigen and negative for vimentin and muscle-specific actin. Some Bbs had residual ghost nuclear shadows. Electron microscopy revealed cellular skeletons with residual tonofilaments enmeshed within a loose cytoskeleton matrix and nuclei with variable degrees of degeneration.

CONCLUSION

Special stains, immunohistochemistry and electron microscopy indicated that Bbs represent parabasal/intermediate squamous cells exhibiting various degree of degeneration. In general, Bbs appear to be of no clinical significance except as a source of potential diagnostic error.

The spatial orientation of the essential amino acid residues arginine and aspartate within the alpha1beta1 integrin recognition site of collagen IV has been resolved using fluorescence resonance energy transfer

The interaction of collagen IV with cells is mediated mainly by the integrin alpha1beta1. The recognition site has been located to a segment of the triple-helical domain 100 nm away from the N terminus of the collagen molecule. The three essential amino acid residues of the alpha1beta1 binding site, arginine alpha2(IV)461 and the two aspartate residues alpha1(IV)461, are all located on different chains. Since the spatial array of the three residues depends on the stagger of the chains within the triple helix, the stagger has been elucidated using fluorescence resonance energy transfer with phenylalanine alpha1(IV)473 and tryptophan alpha2(IV)479 as the fluorescent donor/acceptor pair. The distance R between phenylalanine and tryptophan was determined by analysis of the energy transfer efficiency, E, and the orientation factor, kappa(2). In parallel, distance R and orientation factor, kappa(2 )were also calculated from the coordinates of the triple helix. Comparison of the calculated and empirically determined values unequivocally showed the stagger to be alpha1'alpha1alpha2. This arrangement of the three alpha chains describes the conformation of the alpha1beta1 integrin recognition site, that is the distinct orientation of the side-chains of the essential residues aspartate and arginine in respect to the helix axis.

Herpesvirus 6 variant A infection after heart transplantation with giant cell transformation in bile ductular and gastroduodenal epithelium

Herpesvirus 6 (HHV-6) is a ubiquitous virus known to cause febrile syndromes and exanthema subitum in children. Less commonly, and particularly in organ transplant recipients, it may result in hepatitis, bone marrow suppression, interstitial pneunonitis, and meningoencephalitis. This report expands the spectrum of clinical disease associated with HHV-6 by documenting viral infection in a 44-year-old heart transplant recipient presenting with gastroduodenitis, pancreatitis, and hepatitis. On histopathologic examination, the gastric, duodenal, and bile ductular epithelium showed a multinucleate giant cell transformation similar to the cytopathic effect caused by the virus in human T-lymphocytes infected in vitro. Electron microscopy showed herpes particles with a thick tegument layer in the duodenum. Polymerase chain reaction amplified HHV-6 variant A sequences from multiple sites. Serology confirmed the presence of an acute HHV-6 infection. Thus, HHV-6 variant A can cause gastroduodenitis and pancreatitis in immunosuppressed individuals. Multinucleate giant cells and enveloped virions with a prominent tegument can be used as morphologic criteria to raise the possibility of HHV-6 infection in human biopsy tissue.

The recognition sites of the integrins alpha1beta1 and alpha2beta1 within collagen IV are protected against gelatinase A attack in the native protein

The susceptibility of three different solubilized forms of type IV collagen to gelatinase A cleavage and the concomitant effects on cell and integrin binding have been assessed. Dithiothreitol-solubilized Engelbreth-Holm Swarm (EHS) type IV collagen with disrupted intramolecular disulfide bonds in the CB3[IV] region was cleaved N-terminally to the CB3[IV] region into the two characteristic 100-300-nm fragments at 30 degrees C and was totally degraded at 37 degrees C. This was reflected in the partial or total loss of the alpha1beta1 and alpha2beta1 integrin binding sites within this region. The ability of gelatinase A to cleave EHS type IV collagen preparations with intact interchain disulfide bonds in CB3[IV] only occurred at higher temperatures. Furthermore, no effect on binding of cells or isolated integrins to the gelatinase-treated collagen could be detected after treatment at 37 degrees C. Dimeric collagen IV of human placenta with intact disulfide bonds in the CB3[IV] region was not degraded at all by gelatinase A at 37 degrees C.

Typhoid fever in the park: epidemiology of an outbreak at a cultural interface

The number of reported outbreaks of typhoid fever in the United States has recently increased. Only six were reported from 1980-1989, but seven outbreaks were reported in 1990. In August 1990, health officials in Montgomery County, Maryland, were notified of two cases of typhoid fever among persons who had attended both a family picnic attended by 60 persons and a Latin Food Festival attended by 100,000 people. We obtained interviews, blood and stool cultures, and Vi serologies from attendees at and food handlers for the picnic. We defined cases as culture-confirmed or probable. Of the 60 picnic attendees, 24 (40%) had cases, of which 16 were culture confirmed. Those who ate potato salad were at increased risk of disease (17/32 vs. 6/28, relative risk [RR] = 2.5, 95% confidence interval [CI] 1.1-5.4). Picnic attendees who also attended the Latin Food Festival were not at significantly greater risk of disease than those who did not, (11/22 vs. 13/38, RR = 1.5, CI = 0.8-2.7) and we found no evidence of disease among other festival attendees. The potato salad was prepared with intensive handling and without adequate temperature control by a recent immigrant from El Salvador who was asymptomatic, did not attend the picnic, had Salmonella typhi (S. typhi) in her stool, and had elevated Vi antibodies, strongly suggestive of the carrier state. Outbreaks of typhoid fever are a threat for cosmopolitan communities. While currently available control measures are unlikely to prevent all outbreaks, thorough investigation can identify previously unrecognized carriers.

The function of the NC1 domains in type IV collagen

At its C terminus, the collagen IV molecule bears a globular NC1 domain, to which two functions have been assigned. In the macromolecular network of collagen IV, two molecules are connected via their NC1 domains, which form a hexameric complex, stabilized by intermolecular disulfide bonds. In addition, the NC1 domains are thought to be responsible for chain selection and assembly. In order to understand the role of the NC1 domains during these steps, hexameric complexes were isolated and further investigated. SDS-polyacrylamide gel electrophoresis and Western blot revealed disulfide-linked alpha 1 (IV)NC1 and alpha 2(IV)NC1 homodimers but no heterodimers. The hexamers were dissociated at low pH, separated into monomers and dimers, and submitted to reconstitution experiments. Only alpha 1(IV)NC1 dimers were able to reconstitute a hexameric complex. alpha(IV)-NC1 and alpha 2(IV)NC1 monomers as well as the alpha 2(IV)NC1 dimers showed only a low tendency to form complexes. It is assumed that during formation of the collagen IV network, lateral aggregation of the molecules via the triple helical domains brings the C termini of two molecules into close vicinity and that subsequently the weak interactions observed between the NC1 subdomains provide the correct alignment for a disulfide exchange. It is, however, questionable whether the low affinity between the NC1 subdomains alone is sufficient for chain assembly and alignment of the alpha(IV) chains before molecule formation.

Erythromycin shortens orocaecal transit time in diabetic male subjects: a double-blind placebo-controlled study

BACKGROUND

The effects of erythromycin on small bowel motility are controversial. Orocaecal transit time (OCTT) is considered to be a valid measure of small bowel motility.

METHODS

We studied the effect of erythromycin on OCTT in diabetic male subjects in a double-blind placebo-controlled crossover fashion. After an overnight fast, subjects received erythromycin 500 mg, 250 mg or placebo, on 3 different days. A standard solid meal containing 20 g lactulose was administered 30 min after the erythromycin ingestion. Exhaled breath was collected and hydrogen concentration was assessed over 5 h. Breath hydrogen concentrations for each session were analysed over time by a generalized logistic function generating a sigmoidal curve. Front transit time was recorded as the time point when a sustained rise in breath hydrogen concentration of at least 5 p.p.m. was first observed.

RESULTS

The mean +/- S.E.M. time taken for the front of the meal to reach the caecum was 92.5 +/- 9.5, 86.1 +/- 16.5 and 62.3 +/- 12.1 min for placebo, erythromycin 250 mg and erythromycin 500 mg, respectively. The OCTT was significantly decreased with erythromycin 500 mg compared to placebo (P < 0.05).

CONCLUSION

Oral administration of 500 mg erythromycin has prokinetic effect on orocaecal transit in male patients with diabetes mellitus.

Characterization of a type IV collagen major cell binding site with affinity to the alpha 1 beta 1 and the alpha 2 beta 1 integrins

The aim of this investigation was to identify the domains of type IV collagen participating in cell binding and the cell surface receptor involved. A major cell binding site was found in the trimeric cyanogen bromide-derived fragment CB3, located 100 nm away from the NH2 terminus of the molecule, in which the triple-helical conformation is stabilized by interchain disulfide bridges. Cell attachment assays with type IV collagen and CB3 revealed comparable cell binding activities. Antibodies against CB3 inhibited attachment on fragment CB3 completely and on type IV collagen to 80%. The ability to bind cells was strictly conformation dependent. Four trypsin derived fragments of CB3 allowed a closer investigation of the binding site. The smallest, fully active triple-helical fragment was (150)3-amino acid residues long. It contained segments of 27 and 37 residues, respectively, at the NH2 and COOH terminus, which proved to be essential for cell binding. By affinity chromatography on Sepharose-immobilized CB3, two receptor molecules of the integrin family, alpha 1 beta 1 and alpha 2 beta 1, were isolated. Their subunits were identified by sequencing the NH2 termini or by immunoblotting. The availability of fragment CB3 will allow for a more in-depth study of the molecular interaction of a short, well defined triple-helical ligand with collagen receptors alpha 1 beta 1 and alpha 2 beta 1.

Anionic complex-carbohydrate units of human thyroglobulin

Human thyroglobulin (hTG) contains sulfate in chondroitin 6-sulfate chains and in complex carbohydrates. In this study the sulfate-containing complex carbohydrates were characterized by the number of sulfate and sialic acid residues that they contain. Samples of normal and nodular thyroid tissue were incubated for 16 h in [35S]sulfate-containing medium, and hTG was purified from the tissues and the media. Complex carbohydrates were enzymatically removed from hTG. Subsequent analysis on an HPLC anion exchange column at pH 2.2 separated the carbohydrate units according to their number of negative charges. Sulfate-containing peaks were monitored by radioactivity, and sialic acid-containing peaks were identified by their shift to lower charge after treatment with neuraminidase. Peaks corresponding to sialic acid-free carbohydrate units with one to four sulfates were identified. Also, carbohydrate units with two and three negative charges containing both sulfate and sialic acid were present. In the nodular tissue of one patient there were more sulfated units with higher charge, especially units containing sialic acid. In this patient the proportion of sulfated polyvalent units with sialic acid was 22.4% for normal and 64.6% for nodular tissue. No difference in the composition of the charged units between the tissues and their corresponding media was seen, making it unlikely that the sulfate-containing carbohydrates play a role in hTG release. It is concluded that hTG contains complex carbohydrate units with up to four sulfate groups and units with both sulfate and sialic acid. In some patients, the sulfate-containing anionic carbohydrate units of hTG from normal and nodular thyroid tissue are different.

Illustration of the effects of long-term xamoterol therapy on the time course of left ventricular pressure

Detailed left ventricular haemodynamic investigations were performed in eight patients with New York Heart Association (NYHA) Class II heart failure, eight with NYHA Class III heart failure with an ejection fraction less than 35%, and six with severe heart failure. Xamoterol (200 mg b.d. for 3 months) caused a fall in left ventricular end-diastolic pressure, an increase in dP/dTmax and a shorter systole in all groups of patients.

Crystals of the NC1 domain of human type IV collagen

Crystals of the non-collagenous C-terminal region (NC1) of type IV collagen have been obtained from human placenta. These crystals diffract to 2.0 A, and belong to space group P22(1)2(1), with cell dimensions a = 81 A, b = 158 A, c = 138 A, alpha = beta = gamma = 90 degrees. The crystals contain one hexamer in the asymmetric unit; they are very stable with respect to X-rays.

Pulmonary gas exchange in humans during normobaric hypoxic exercise

Previous studies (J. Appl. Physiol. 58: 978-988 and 989-995, 1985) have shown both worsening ventilation-perfusion (VA/Q) relationships and the development of diffusion limitation during heavy exercise at sea level and during hypobaric hypoxia in a chamber [fractional inspired O2 concentration (FIO2) = 0.21, minimum barometric pressure (PB) = 429 Torr, inspired O2 partial pressure (PIO2) = 80 Torr]. We used the multiple inert gas elimination technique to compare gas exchange during exercise under normobaric hypoxia (FIO2 = 0.11, PB = 760 Torr, PIO2 = 80 Torr) with earlier hypobaric measurements. Mixed expired and arterial respiratory and inert gas tensions, cardiac output, heart rate (HR), minute ventilation, respiratory rate (RR), and blood temperature were recorded at rest and during steady-state exercise in 10 normal subjects in the following order: rest, air; rest, 11% O2; light exercise (75 W), 11% O2; intermediate exercise (150 W), 11% O2; heavy exercise (greater than 200 W), 11% O2; heavy exercise, 100% O2 and then air; and rest 20 minutes postexercise, air. VA/Q inequality increased significantly during hypoxic exercise [mean log standard deviation of perfusion (logSDQ) = 0.42 +/- 0.03 (rest) and 0.67 +/- 0.09 (at 2.3 l/min O2 consumption), P less than 0.01]. VA/Q inequality was improved by relief of hypoxia (logSDQ = 0.51 +/- 0.04 and 0.48 +/- 0.02 for 100% O2 and air breathing, respectively). Diffusion limitation for O2 was evident at all exercise levels while breathing 11% O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary gas exchange in humans during exercise at sea level

Previous studies have shown both worsening ventilation-perfusion (VA/Q) relationships and the development of diffusion limitation during exercise at simulated altitude and suggested that similar changes could occur even at sea level. We used the multiple-inert gas-elimination technique to further study gas exchange during exercise in healthy subjects at sea level. Mixed expired and arterial respiratory and inert gas tensions, cardiac output, heart rate, minute ventilation, respiratory rate, and blood temperature were recorded at rest and during steady-state exercise in the following order: rest, minimal exercise (75 W), heavy exercise (300 W), heavy exercise breathing 100% O2, repeat rest, moderate exercise (225 W), and light exercise (150 W). Alveolar-to-arterial O2 tension difference increased linearly with O2 uptake (VO2) (6.1 Torr X min-1 X 1(-1) VO2). This could be fully explained by measured VA/Q inequality at mean VO2 less than 2.5 l X min-1. At higher VO2, the increase in alveolar-to-arterial O2 tension difference could not be explained by VA/Q inequality alone, suggesting the development of diffusion limitation. VA/Q inequality increased significantly during exercise (mean log SD of perfusion increased from 0.28 +/- 0.13 at rest to 0.58 +/- 0.30 at VO2 = 4.0 l X min-1, P less than 0.01). This increase was not reversed by 100% O2 breathing and appeared to persist at least transiently following exercise. These results confirm and extend the earlier suggestions (8, 21) of increasing VA/Q inequality and O2 diffusion limitation during heavy exercise at sea level in normal subjects and demonstrate that these changes are independent of the order of performance of exercise.

Effects of dobutamine and sulmazol (AR-L115 BS) on myocardial metabolism and coronary, femoral, and renal blood flows: a comparative study in normal dogs and in dogs with chronic volume overload

We compared the hemodynamic and metabolic effects of dobutamine and sulmazol (AR-L115 BS) in normal dogs and in dogs with chronic volume overload. In both cases, the doses of dobutamine and sulmazol were adapted to produce comparable increases in two indices of inotropic state, peak (+) left ventricular dP/dt and dP/dt normalized by a developed pressure of 40 mm Hg. In normal dogs, both drugs had similar effects on myocardial oxygen consumption, myocardial high-energy phosphate stores, and renal or femoral blood flows; in addition, mean aortic pressure (129 +/- 8 to 114 +/- 10 mm Hg; p less than 0.002), the renal vascular resistance (--18%; p less than 0.005), and the coronary vascular resistance (--30%; p less than 0.05) were all decreased significantly during sulmazol administration. In chronic volume overload, the changes in renal and femoral blood flows and in myocardial high-energy phosphate stores induced by dobutamine or sulmazol were again similar. However, sulmazol still decreased mean aortic pressure (--20 +/- 5 mm Hg; p less than 0.002) and markedly reduced the left ventricular filling pressure (--40%; p less than 0.006), while these parameters were not significantly modified after dobutamine. Myocardial oxygen consumption was unchanged after sulmazol but increased slightly with dobutamine. Finally, the frequency of ventricular premature beat was unchanged by sulmazol but increased after dobutamine. In conclusion, sulmazol is likely to be superior to dobutamine to stimulate a failing left ventricle when clinical status is characterized by markedly elevated filling pressures. It might also be superior when the coronary vascular reserve is reduced or in the presence of ventricular arrhythmias.

Restrictive ventilatory pattern in precapillary pulmonary hypertension

Patients with precapillary pulmonary hypertension (PPH) have classically been reported to have normal pulmonary mechanical function. We reviewed spirometric data from 8 patients with primary pulmonary hypertension and from 17 patients with chronic thromboembolic pulmonary hypertension. All patients had undergone right heart catheterization and pulmonary angiography. Five of the 8 patients with primary pulmonary hypertension demonstrated a severe restrictive ventilatory pattern with a mean vital capacity (VC) of 50.4% predicted and a mean total lung capacity (TLC) of 64.3% predicted. Five of the 17 patients with chronic thromboembolic pulmonary hypertension manifested a restrictive pattern with a mean VC of 68.0% predicted and a mean TLC of 75.3% predicted. We conclude that restrictive ventilatory defects occur more frequently than previously described in patients with PPH. The physiologic mechanism responsible for the restrictive ventilatory pattern is not clear.

Cardiovascular effects of AR-L115 BS in conscious dogs with and without chronic congestive heart failure

AR-L115 BS is a phenyl-imidazo-pyridine derivative that combines positive inotropic and vasodilator properties. To analyze the mechanisms of action of AR-L115 in the presence or absence of heart failure, we administered it intravenously to conscious dogs (seven normals and eight with a volume-overload heart failure). In normals, at a plasma level around 1,000 ng/ml, AR-L115 BS increased left ventricular (LV) peak (+) dP/dt (+48%; p less than 0.02) and heart rate (+29 beats/min; p less than 0.05) without altering significantly cardiac filling pressures or cardiac output. The mean aortic pressure and the systemic vascular resistances (-20%; p less than 0.02) were reduced, but plasma renin activity (PRA) was unchanged. In heart failure, the same plasma level increased peak (+) dP/dt by 36% (p less than 0.01), but heart rate stayed unchanged. Mean aortic pressure, systemic vascular resistances (-20%; p less than 0.01), and LV end-diastolic pressure (-9.1 mm Hg; p less than 0.01) all dropped significantly, while cardiac output increased slightly; PRA did not rise significantly. After beta-blockade, the increases in peak (+) dP/dt and the changes in systemic vascular resistances were markedly reduced. In conclusion, AR-L115 BS has strong positive inotropic and vasodilator effects, both of which are partially dependent on the level of the sympathetic tone in the intact animal. These combined properties improve hemodynamics in heart failure; this improvement is already significant at relatively low plasma levels, at which deleterious changes in heart rate or PRA are absent.