Pulmonary vascular permeability in interstitial lung disease. A positron emission tomographic study

We evaluated pulmonary vascular permeability with positron emission tomography (PET) in 16 patients with interstitial lung disease (ILD) by measuring the pulmonary transcapillary escape rate (PTCER) for transferrin labeled with gallium-68. In patients with active ILD, defined by lung biopsy or clinical criteria, mean PTCER was significantly greater than in normal subjects (118 +/- 46 versus 21 +/- 11 x 10(-4) min-1, respectively, p less than 0.05). Mean PTCER in patients with inactive ILD, in contrast, was not different from that in normal subjects (32 +/- 10 x 10(-4) min-1, p = NS). Thus, these data suggest that PET measurements of PTCER might serve as an index of disease activity in patients with ILD.

Effects of disease stage and zidovudine therapy on the detection of human immunodeficiency virus type 1 in semen

OBJECTIVE

To determine the prevalence and temporal expression of infectious human immunodeficiency virus type 1 (HIV-1) in the semen of HIV-1 seropositive men and to determine whether the detection of HIV-1 in semen is associated with disease stage, zidovudine treatment status, or other clinical factors.

DESIGN

A microculture technique was used to detect infectious HIV-1 in semen from a cohort of 95 seropositive men. In addition, semen cultures were performed monthly for at least 6 months for 14 of the men. Information was obtained by interview and extracted from medical records to identify clinical variables associated with HIV-1 in semen.

PATIENTS

Sixty HIV-1 seropositive homosexual men participating in clinical studies at the Fenway Community Health Center, Boston, Mass, and 35 HIV seropositive bisexual or heterosexual men participating in the California Partner Study of the University of California, San Francisco.

MAIN OUTCOME MEASURES

Semen HIV-1 culture results, seminal leukocyte counts, Centers for Disease Control (CDC) disease stage, peripheral CD4+ cell counts, zidovudine therapy, HIV risk category.

RESULTS

In the cross-sectional study, HIV-1 was cultured from the semen of nine (9%) of 95 men. Factors associated with detection of HIV-1 in semen were peripheral CD4+ cell counts of 0.20 x 10(9)/L (200/microL) or less (adjusted odds ratio [OR], 23.33; 95% confidence interval [Cl], 2.89 to 175.63); symptomatic (CDC class IV) disease (adjusted OR, 6.56; 95% Cl, 1.02 to 66.76); and seminal leukocytosis (greater than 1 x 10(9) white blood cells per liter of semen) (adjusted OR, 7.02; 95% Cl, 1.28 to 39.29). Zidovudine therapy was associated with decreased detection of HIV-1 in semen (adjusted OR, 0.04; 95% Cl, 0.00 to 0.63). In the longitudinal study of 14 men who had neither peripheral CD4+ cells counts of 0.20 x 10(9)/L or less nor seminal leukocytosis, seminal HIV-1 was detected in at least one sample from six men (43%).

CONCLUSION

HIV-1 is more commonly found in semen from men with advanced HIV-1 infection and seminal leukocytosis but can also be cultured from semen of men with neither of these conditions. Zidovudine therapy may decrease the prevalence and/or titer of seminal HIV-1. However, all HIV-1-infected persons should continue to assume that they are potentially infectious through sexual contact.

Changes in competence determine the timing of two sequential glucocorticoid effects on sympathoadrenal progenitors

We have studied the control of adrenal chromaffin cell development by glucocorticoids (GCs), in a reconstituted in vitro system. The development of the chromaffin phenotype involves two sequential, GC-dependent events: the decision not to become a sympathetic neuron, and the decision to express the epinephrine-synthesizing enzyme, phenylethanolamine-N-methyltransferase (PNMT). Both decisions appear to be mediated by the type II GC receptor. Competence to express PNMT develops on a schedule in vitro which parallels that seen in vivo, but only in progenitors that have first failed to undergo neuronal differentiation. The schedule of PNMT induction is thus controlled by the time of appearance of neither the inducing signal nor its receptor, as previously suggested, but rather by a cell-intrinsic timed process in chromaffin precursors. The two effects of GCs are pharmacologically distinct, suggesting that the GC receptor may interact differently with different genes in the same cell, in a manner that changes with development.

DNA binding and transcriptional regulatory activity of mammalian achaete-scute homologous (MASH) proteins revealed by interaction with a muscle-specific enhancer

The MASH genes are vertebrate homologues of achaete-scute, genes required for neuronal determination in Drosophila. The sequence of MASH1 and MASH2 contains a basic helix-loop-helix (bHLH) motif that is present in other transcriptional regulators such as MyoD and E12. In the absence of an authentic target for the MASH proteins, we examined their DNA binding and transcriptional regulatory activity by using a binding site (the E box) from the muscle creatine kinase (MCK) gene, a target of MyoD. Like myogenic bHLH proteins, the MASH proteins form heterooligomers with E12 that bind the MCK E box with high affinity in vitro. Unexpectedly, however, MASH1 and MASH2 also activate transcription of both exogenous and endogenous MCK in transfected C3H/10T1/2 fibroblasts. However, they do not induce myogenesis. Myogenic activity is not exclusively a property of the MyoD basic region, as substitution of this domain fails to confer myogenic activity on MASH1. These data suggest that different bHLH proteins may activate overlapping but distinct sets of target genes in the same cell type.

Evidence of embryo- and trophoblast-toxic cellular immune response(s) in women with recurrent spontaneous abortion

OBJECTIVE

The purpose of this study was to determine whether reproductive antigens stimulate lymphocytes and macrophages from women with recurrent abortion to secrete factors that are toxic to preimplantation embryos or trophoblast cells in vitro.

STUDY DESIGN

Mononuclear cells were isolated from 30 fertile controls and 300 nonpregnant women being evaluated for recurrent abortion. Supernatants generated from these cells after separate culture with sperm and trophoblast antigen extracts were added to two-cell mouse embryo cultures and trophoblast proliferation assays. Toxicity was assumed when the median percentage of embryos developing to blastocysts or trophoblast proliferation was less than or equal to 50% of control values. Both parametric and nonparametric statistical methods were used where appropriate.

RESULTS

Mouse embryo development and/or trophoblast proliferation were significantly inhibited by supernatants from trophoblast and/or sperm antigen-activated peripheral blood leukocyte cultures from a majority of 300 women with recurrent abortion but not from 30 women with normal reproductive histories. The mouse blastocyst development assay was more sensitive than the trophoblast proliferation assay in determining toxic factor production. Embryo-toxic factors were produced by activated leukocyte cultures from 90% of 180 women with a history of recurrent abortion of unexplained etiology, whereas trophoblast-inhibitory factors were detected in 50% of women from the same group. The embryo-toxic factor(s) was heat labile, had a molecular weight(s) between 10 and 30 kd, and was absorbed out by passage through affinity columns containing anti-interferon gamma beads.

CONCLUSION

We conclude that recurrent abortion in some women is associated with embryo- and/or trophoblast-toxic factor production in response to stimulation by sperm or trophoblast antigens and that the principal factor may involve the 18 kd, heat-labile, T-lymphocyte cytokine interferon gamma. This study suggests a new cause of recurrent abortion.

Social integration of older persons with mental retardation in residential facilities

The findings from a study of the social integration of a national sample of 370 older persons with mental retardation were reviewed. Individuals were selected from a national sample of all facilities owned, operated, or licensed by developmental disabilities agencies having one or more persons 63 years of age or older with mental retardation (N = 235). Facilities included foster care, small group homes (3 to 15 residents), large private facilities, and large state-operated facilities. Information was obtained on resident activities and relations considered to be indicators of social integration through extensive questionnaires completed by primary caregivers. Comparisons of the differences in community integration among residents living in different types of residential facilities were presented. The relative contribution of individual and facility characteristics to the social integration of older persons with mental retardation was explored with hierarchical multiple regression analysis.

Cryptococcal disease presenting as cellulitis

Three immunocompromised patients presented with cellulitis as the primary manifestation of cryptococcal disease. Two were recipients of cadaveric renal transplants who were receiving immunosuppressive drug therapy. The other patient had profound lymphopenia and severe hypoalbuminemia due to intestinal lymphangiectasia. All had failed to respond to empiric therapy for presumed bacterial cellulitis before results of skin biopsy or aspiration were available for the correct diagnosis to be made. With administration of systemic antifungal therapy, two patients survived. Although other forms of cryptococcal involvement of the skin are not rare, cellulitis is seldom considered to be a cutaneous manifestation of the disease. Our cases and a review of the English-language literature indicate that Cryptococcus neoformans must be included in the differential diagnosis of cellulitis in immunocompromised patients and that the presence of cryptococcal cellulitis suggests disseminated cryptococcal disease. Prompt diagnosis and treatment may dramatically reduce mortality.

Effects of nicotine on spatial memory deficits in rats with septal lesions

Impaired septohippocampal function has been implicated in the memory deficits associated with Alzheimer's disease (AD), and septal lesions have been used to model the cognitive deficits associated with AD. In this study, we assessed the effects of systemic administration of nicotine on lesion-induced deficits in the acquisition of a spatial discrimination version of the Morris water maze. Rats with radiofrequency lesions of the medial septum were required to learn which of two visible platforms in a pool of water provided a means of escape. On each of the first 4 days of training, the rats received an injection of (-)nicotine (0, 0.1 or 0.3 mg/kg, i.p.) before training. Nicotine markedly improved the performance of septal rats. This enhanced performance was maintained in rats subsequently tested 1 and 15 days later without additional drug treatment. Septal rats initially trained under nicotine were impaired, however, when the platform locations were reversed and training was conducted under saline. Our findings suggest that nicotinic receptor stimulation might be useful in the treatment of cognitive deficits.

Use of an intramedullary rod for the treatment of congenital pseudarthrosis of the tibia

The use of an intramedullary rod as described by Williams, combined with implantation of an autogenous bone graft, resulted in union of an established congenital pseudarthrosis of the tibia in nine of ten patients. One patient needed additional bone-grafting before union occurred. The average age at the time of the operation was five years and three months. A rod of the appropriate length was inserted at the site of the non-union, antegrade through the distal part of the tibia and the hindfoot and then retrograde through the proximal fragment. This resulted in splinting of the tibia, ankle, and subtalar joints. Solid osseous union occurred an average of six months after the procedure in all ten patients. Five patients had a refracture of the tibia after the initial consolidation. Three of the five needed one or more additional operative procedures; one was managed with a cast; and one patient, who had been followed for four years before the refracture, did not return for treatment of the refracture. As is the plan with this method of treatment, the distal part of the tibia grew off the rod and the distal tip of the rod was located proximal to the foot and ankle, or it was located more proximally than it had been at the operation, in six patients. The rod was removed from three patients. At an average of six years, all ten patients were able to walk without pain.

Human vaginal leukocytes and the effects of vaginal fluid on lymphocyte and macrophage defense functions

OBJECTIVES

The purpose of this study was to quantify, characterize, and further define the role of vaginal white blood cells in defense mechanisms and human immunodeficiency virus infection.

STUDY DESIGN

Vaginal lavages were obtained from five healthy women throughout three menstrual cycles. Lymphocyte subpopulations, macrophages, and granulocytes were characterized and quantified by an immunohistologic technique. Vaginal lavage fluid was added to peripheral blood mononuclear cells, and effects on cell viability, lymphocyte proliferation, macrophage phagocytosis, and expression of various cell surface molecules critical to immunologic functions were assessed. Data were analyzed by Student's t test.

RESULTS

Few lymphocytes were found at any stage of the menstrual cycle; however, granulocytes and macrophages were abundant at menstruation and present at low levels through the proliferative phase. Vaginal lavage fluid collected during menses, at midcycle, and after coitus suppressed mitogen-induced lymphocyte proliferation but had no effect on surface expression of human leukocyte antigen or CD4 antigens, or on macrophage function. Likewise, low pH (less than 5.0) medium significantly inhibited lymphocyte proliferation but had no effect on macrophage phagocytosis. The spermicide nonoxynol 9 was toxic to both lymphocytes and macrophages.

CONCLUSION

White blood cells, including lymphocytes and macrophages, are infrequently present in cervicovaginal secretions of healthy women except during menses; the vaginal environment may effect their function.

Induction and repression of mammalian achaete-scute homologue (MASH) gene expression during neuronal differentiation of P19 embryonal carcinoma cells

MASH1 and MASH2, mammalian homologues of the Drosophila neural determination genes achaete-scute, are members of the basic helix-loop-helix (bHLH) family of transcription factors. We show here that murine P19 embryonal carcinoma cells can be used as a model system to study the regulation and function of these genes. MASH1 and MASH2 display complementary patterns of expression during the retinoic-acid-induced neuronal differentiation of P19 cells. MASH1 mRNA is undetectable in undifferentiated P19 cells but is induced to high levels by retinoic acid coincident with neuronal differentiation. In contrast, MASH2 mRNA is expressed in undifferentiated P19 cells and is repressed by retinoic acid treatment. These complementary expression patterns suggest distinct functions for MASH1 and MASH2 in development, despite their sequence homology. In retinoic-acid-treated P19 cells, MASH1 protein expression precedes and then overlaps expression of neuronal markers. However, MASH1 is expressed by a smaller proportion of cells than expresses such markers. MASH1 immunoreactivity is not detected in differentiated cells displaying a neuronal morphology, suggesting that its expression is transient. These features of MASH1 expression are similar to those observed in vivo, and suggest that P19 cells represent a good model system in which to study the regulation of this gene. Forced expression of MASH1 was achieved in undifferentiated P19 cells by transfection of a cDNA expression construct. The transfected cells expressing exogenous MASH1 protein contained E-box-binding activity that could be super-shifted by an anti-MASH1 antibody, but exhibited no detectable phenotypic changes. Thus, unlike myogenic bHLH genes, such as MyoD, which are sufficient to induce muscle differentiation, expression of MASH1 appears insufficient to promote neurogenesis.

Molecular cloning and characterization of the RNA packaging-defective retrovirus SE21Q1b

The nonconditional RNA packaging mutant SE21Q1b contains cis- and trans-acting defects which cause cellular mRNA, rather than viral genomic RNA, to be nonspecifically packaged into SE21Q1b viral particles. Using genomic libraries of the c-SE21Q1b quail cell line, we have been able to construct a molecular clone of the SE21Q1b provirus. Upon transfection into primary quail embryo fibroblasts, the SE21Q1b molecular clone is able to recapitulate the nonspecific RNA packaging phenotype of the c-SE21Q1b cell line. The RNA packaging phenotypes displayed by several SE21Q1b/avian sarcoma-leukemia virus hybrid provirus constructs have further indicated that sequences responsible for the altered RNA packaging phenotype of SE21Q1b are localized in the left third of the SE21Q1b proviral genome. DNA sequence analysis of this region has revealed that the 5' SE21Q1b deletion has removed 179 bp from the SE21Q1b left long terminal repeat and leader regions. Several differences were detected at the carboxyl terminus of the deduced SE21Q1b nucleocapsid protein sequence in comparison with that of Rous sarcoma virus PR-C. Results of site-directed oligonucleotide mutagenesis experiments indicate, however, that the presence of these residues in the nucleocapsid protein alone is not responsible for the decreased RNA packaging specificity of SE21Q1b.

Colonization of biofilms by bacteria capable of biodegrading sodium dodecyl sulphate (SDS) at clean and polluted riverine sites

Biofilm formation on presterile slate-discs placed at a pristine source site and at three polluted sites located upstream from, at, and down-stream from a sewage-works outfall in a South Wales river, was monitored over 14 days. Viable bacterial cell densities in biofilms increased with time at all sites but more rapidly at the polluted sites, and stabilized after 1-4 days at levels equal to those of stones indigenous to the corresponding sites, and similar to those seen in other comparable pristine and polluted rivers. Biofilm cell densities were elevated about 1,000-fold at the sewage works outfall compared with the site immediately upstream. Downstream from the outfall, the cell densities were intermediate between the upstream and outfall values. Epilithon resuspended from the slates during colonization was tested for its capacity to biodegrade the surfactant sodium dodecyl sulphate (SDS) in die-away tests. No biodegradation of this common pollutant was observed for the samples from the pristine source. In contrast, even after only 1 day, all polluted sites produced samples capable of biodegrading SDS. Longer exposure in the river led to more rapid onset of biodegradation in the die-away tests, indicating an adaptation mechanism(s). Die-away kinetics were fitted by computerized non-linear regression analysis to one of several models. The model of best fit involved biodegradation of SDS by a bacterial population growing at the expense of endogenous carbon. The regression parameter reflecting SDS-degrading activity of the epilithic samples increased markedly during Days 0-4 for all three polluted sites. The stabilized values (Days 4-14) increased from the upstream site to the outfall, then decreased to intermediate values downstream. Although this pattern corresponded to the changes in viable cell numbers, the effect of the sewage input was less marked for the SDS-degrading activities than for bacterial cell densities. In addition, there was little variation in growth characteristics throughout colonization at all three polluted sites. Collectively the results indicate that the observed adaptation during exposure in the river is attributable to colonization of the epilithon by an existing SDS-degrading population, rather than the acquisition or adaptation of this biodegradative capability.

Evidence that enteric neurons may derive from the sympathoadrenal lineage

The first neurons that differentiate in the embryonic foregut of mammals transiently express catecholamine biosynthetic enzymes and accumulate catecholamine. Since this transmitter is found predominantly in cells of the sympatho-adrenal (SA) lineage, it has been suggested that enteric and sympathetic neurons may derive from the same progenitor. Enteric neurons would then lose the catecholamine phenotype during further development, as the two lineages diverge. We have further investigated this possibility using the SA1 monoclonal antibody that binds selectively to SA progenitor cells in the embryonic rat. We find that SA1 binds to the tyrosine hydroxylase+, neurofilament+, and SCG10+ cells of the Embryonic Day 14.5 (E14.5) rat foregut. We also find that a marker for later neuronal differentiation in the SA lineage, B2, also appears in the myenteric plexus concomitant with the loss of SA1 staining. Thus, at least some enteric neuronal precursors may exhibit the SA1----B2 antigenic switch previously observed in developing sympathetic neurons at E14.5. SA1 staining in the foregut partially overlaps with staining for neuropeptide Y, vasoactive intestinal polypeptide, and serotonin. These results support the hypothesis that enteric and sympathetic neurons derive from a common progenitor and that as the markers for the SA lineage are down-regulated, the many types of enteric neurons begin to differentiate.

Co-expression of multiple neurotransmitter enzyme genes in normal and immortalized sympathoadrenal progenitor cells

We have examined the expression of mRNAs encoding five major neurotransmitter-synthesizing enzymes in MAH cells, a clonal cell line derived by retroviral immortalization of a rat embryonic sympathoadrenal progenitor cell. These mRNAs include tyrosine hydroxylase (TH), choline acetyltransferase (ChAT), tryptophan hydroxylase (TpH), and glutamic acid decarboxylases (GADs) 1 and 2. We find that MAH cells express high levels of TH mRNA and low levels of ChAT and TpH mRNAs. Neither GAD1 nor GAD2 mRNAs are detectable using an RNase protection assay with a detection limit of less than one transcript per cell. A similar pattern of mRNA expression is observed in postnatal superior cervical ganglia, adrenal medulla, and in PC12 cells. Transmitter synthesis and accumulation assays indicate that MAH cells can synthesize both catecholamines and acetylcholine. Thus the TH and ChAT mRNAs detected in these cells are likely to be translated into active enzyme. To corroborate these data obtained using MAH cells, we performed similar transmitter synthesis and accumulation assays on sympathoadrenal progenitors directly isolated from E14.5 fetal adrenal glands by fluorescence-activated cell sorting. These progenitor cells also synthesize and accumulate both catecholamines and acetylcholine, albeit to different extents than MAH cells. Both MAH cells and their nonimmortal counterparts are able to increase slightly their cholinergic function upon short-term exposure to CDF/LIF, a factor known to induce acetylcholine synthesis in postmitotic sympathetic neurons. Taken together, these data suggest that progenitor cells in the sympathoadrenal lineage acquire the ability to simultaneously transcribe several different neurotransmitter enzyme genes early in development, prior to their choice of final cell fate. At the same time, the progenitors possess receptors which regulate expression of these genes in response to environmental factors. This ability may permit the cells to choose from several different transmitter phenotypes in response to different environments, as they migrate through the embryo. The persistent transcription of these genes in adult cells, moreover, may in part account for the phenotypic plasticity of cells in this lineage.

Antibody markers identify a common progenitor to sympathetic neurons and chromaffin cells in vivo and reveal the timing of commitment to neuronal differentiation in the sympathoadrenal lineage

Using specific antibody markers and double-label immunofluorescence microscopy, we have followed the fate of progenitor cells in the sympathoadrenal (SA) sublineage of the neural crest in developing rat embryos. Such progenitors are first recognizable in the primordial sympathetic ganglia at embryonic day 11.5 (E11.5), when they express tyrosine hydroxylase. At this stage, the progenitors also coexpress neuronal markers such as SCG 10 and neurofilament, together with a series of chromaffin cell markers called SA 1-5 (Carnhan and Patterson, 1991 a). The observation of such doubly labeled cells is consistent with the hypothesis that these cells represent a common progenitor to sympathetic neurons and adrenal chromaffin cells. Subsequent to E 11.5, expression of the chromaffin markers is extinguished in the sympathetic ganglia but retained by cells within the adrenal gland. Concomitant with the loss of the SA 1-5 immunoreactivity in sympathetic ganglia, a later sympathetic neuron-specific marker, B2, appears. In dissociated cell suspensions, some B2+ cells that coexpress SA 1 are seen. This implies a switch in the antigenic phenotype of developing sympathetic neurons, rather than a replacement of one cell population by another. The SA 1----B2 transition does not occur for the majority of cells within the adrenal primordium. In vitro, most B2+ cells fail to differentiate into chromaffin cells in response to glucocorticoid. Instead, they continue to extend neurites and then die. Taken together, these data imply that the SA 1----B2 transition correlates with a loss of competence to respond to an inducer of chromaffin differentiation. Thus, the development of SA derivatives is controlled both by environmental signals and by changes in the ability of differentiating cells to respond to such signals.

Mammalian achaete-scute homolog 1 is transiently expressed by spatially restricted subsets of early neuroepithelial and neural crest cells

Using monoclonal antibodies, we have examined the expression pattern of MASH1, a basic helix-loop-helix protein that is a mammalian homolog of the Drosophila achaete-scute proteins. In Drosophila, achaete-scute genes are required for the determination of a subset of neurons. In the rat embryo, MASH1 expression is confined to subpopulations of neural precursor cells. The induction of MASH1 precedes, but is extinguished upon, overt neuronal differentiation. MASH1 is expressed in the forebrain by spatially restricted domains of neuroepithelium and in the peripheral nervous system exclusively by precursors of sympathetic and enteric neurons. The features of early and transient expression, in spatially restricted subpopulations of neural precursors, are similar to those observed for achaete-scute. Thus, the amino acid sequence conservation between MASH1 and achaete-scute is reflected in a parallel conservation of cell type specificity of expression, similar to the case of mammalian MyoD and Drosophila nautilus. These data support the idea that helix-loop-helix proteins may represent an evolutionarily conserved family of cell-type determination genes, of which MASH1 is the first neural-specific member identified in vertebrates.

Shared-stimulus driving and connectivity in groups of neurons in the dorsal cochlear nucleus

Extracellular spike discharges were recorded from ensembles of up to five neurons simultaneously in the DCN of guinea pig using solid-state, thin-film, multichannel electrodes having up to five recording sites spanning up to 600 microns. Responses from 73 unit pairs were collected of which 54 had both units responding to pseudorandom wideband noise stimulation. Shared-stimulus driving was present in 78% (42/54) of the unit pairs and could be attributed to an overlap in their spectral sensitivities. Effective connectivity was indicated for 87% (47/54) of the unit pairs. Wideband noise proved more useful than tonebursts for investigating shared-stimulus driving and connectivity because it evoked widespread, but not overly synchronous, responses in the ensembles.

Anatomy of the major fissure: evaluation with standard and thin-section CT

The major fissures of the right and left lungs were studied with standard computed tomography (CT) (10-mm-thick sections) and thin-section CT (2-mm-thick sections) in 50 patients. On standard CT scans, the major fissures were seen in 90%-100% of cases at each of three selected levels. They usually appeared as hypoattenuating bands and less often as lines or hyperattenuating bands. Although in most cases the major fissure was seen as a line on thin-section CT scans, this appearance was more common in the upper portion of the left major fissure than in the upper portion of the right major fissure. A "double-fissure sign" was most frequently seen at the base of the left lung; however, the sign was also seen at higher levels, with approximately equal frequency in the right and left lungs. An incomplete major fissure was noted in the right lung in 32 cases (64%) and in the left lung in 26 cases (52%). The upper and middle portions of the left major fissure were less frequently incomplete than were the comparable portions of the right major fissure. Thin-section CT provided better delineation of the major interlobar fissures than did standard CT.

Choosing the right antibacterial agent. Is 'newer' always better?

The newer antibacterials are proving in some situations to be more effective than the older agents, and it is tempting to choose them. In many instances, however, traditional agents remain the treatment of choice. Major drawbacks of using newer antibacterials include their higher cost by weight, compared with older drugs, and the emergence of resistant organisms or superinfection as a result of overuse. The newer drugs are best reserved for use when older agents would be inadequate.

Artifacts in computed radiography

Storage-phosphor digital radiographic systems are becoming widely used in a variety of diagnostic procedures. The equipment is reliable and produces images of consistently high quality. However, the images may contain artifacts directly related to the digital techniques used, to the phosphor imaging plate, or to radiography in general. This article illustrates many of the artifacts encountered that are specific to computed radiography, some of which can simulate pathologic lesions. Their causes and remedies are discussed briefly.