Allergic contact dermatitis from doxepin cream. One-year patch test clinic experience

BACKGROUND AND DESIGN

Several topical antihistamines are known to cause contact allergy. Premarket predictive patch testing with doxepin cream showed it to have "low risk of irritation and sensitization" on normal human skin. In our patch test clinic, we routinely test topical preparations, and over a recent 1-year period, we patch-tested doxepin cream, the standard screening tray, and other topical preparations on 97 patients with various pruritic dermatoses. When possible, patients with positive reactions to doxepin cream were patch-tested with its ingredients, and repeated open-application use tests were also performed with the product.

RESULTS

Seventeen patients had relevant positive patch test reactions to doxepin cream and 80 had negative reactions. In 13 of the 17 patients with positive reactions, the diagnosis of allergic contact dermatitis to doxepin cream was confirmed by positive patch test reactions to both the active ingredient and the whole formulation of doxepin cream, by an observed positive use test reaction to doxepin cream, or by both. Of 14 patients who completed testing with doxepin cream ingredients, all had positive reactions to the whole formulation, and 12 had positive reactions to doxepin hydrochloride. Repeated open-application use tests with doxepin cream on normal skin resulted in positive eczematous responses in eight of 10 patients. Eight of the 17 patients had concurrent, relevant positive reactions to other patch tests, especially to fabric-finish resins and to ingredients of other topical preparations. Many had long-standing dermatitis, and each had used doxepin cream for several days to 1 year. Two patients appeared to have had systemic contact dermatitis.

CONCLUSIONS

Diagnostic patch test clinic experience illustrates that doxepin cream is a contact sensitizer on inflamed skin. Oral doxepin should be avoided in patients with doxepin contact allergy.

Mutation spectra of TA*, the major photoproduct of thymidylyl-(3'5')-deoxyadenosine, in Escherichia coli under SOS conditions

The biological activity of TA*, the major photoproduct of thymidylyl-(3',5')-deoxyadenosine, has remained speculative since it was identified a decade ago. To determine the mutagenicity of TA* in Escherichia coli, we constructed the replicative form of an M13mp18-derived phage containing TA* in the (-)-strand by polymerase-catalyzed elongation of a TA*-containing 49mer opposite a uracil-containing (+)-strand of the phage. The in vitro synthesis mixture was transfected into an ung+, phr- E.coli host and the progeny were screened with a hybridization probe unique for the (-)-strand. TA* was found to block DNA replication substantially in the absence of SOS, but under SOS, TA* was bypassed more efficiently and was highly mutagenic. Among 56 analyzed (-)-strand progeny from two transfections, 46 (82%) were mutants, including six (11%) tandem mutants. The most abundant mutation was a 3'A-->T substitution (31/46, 56%). The possible biological consequences of TA* formation in the highly conserved TATA box consensus sequence on gene expression are discussed in light of the mutagenicity of TA*.

The structure of d(TpA), the major photoproduct of thymidylyl-(3'5')-deoxyadenosine

Irradiation of the dinucleotide TpdA and TA-containing oligonucleotides and DNA produces the TA* photoproduct which was proposed to be the [2+2] cyclo-addition adduct between the C5-C6 double bonds of the T and the A [Bose,S.N., Kumar,S., Davies,R.J.H., Sethi,S.K. and McCloskey,J.A. (1984) Nucleic Acids Res. 12, 7929-7947]. The proposed structure was based on a variety of spectroscopic and chemical degradation studies, and the assignment of a trans-syn-I stereochemistry was based on an extensive 1H-NMR and molecular modeling study of the dinucleotide adduct [Koning,T.M.G., Davies,R.J.H. and Kaptein,R. (1990) Nucleic Acids Res. 18, 277-284]. However, a number of properties of TA* are not in accord with the originally proposed structure, and prompted a re-evaluation of the structure. To assign the 13C spectrum and establish the bond connectivities of the TA* photoproduct of TpdA [d(TpA)*], 1H-13C heteronuclear multiple-quantum coherence (HMQC) and heteronuclear multiple bond correlation (HMBC) spectra were obtained. The 13C shifts and connectivities were found to be inconsistent with the originally proposed cyclobutane ring fusion between the thymine and adenine, but could be explained by a subsequent ring-expansion reaction to give an eight-membered ring valence isomer. The new structure for the d(TpA)* resolves the inconsistencies with the originally proposed structure, and could have a stereochemistry that arises from the anti, anti glycosyl conformation found in B form DNA.

Mutation spectra of M13 vectors containing site-specific Cis-Syn, Trans-Syn-I, (6-4), and Dewar pyrimidone photoproducts of thymidylyl-(3'-->5')-thymidine in Escherichia coli under SOS conditions

The mutations spectra of cis-syn, trans-syn-I, (6-4), and Dewar pyrimidone photoproducts of the TT site of AATTAA and TATTAT in the (-) strand of a heteroduplex M13 vector were obtained in an excision and photoreversal repair deficient Escherichia coli host under SOS conditions. Oligonucleotides containing site-specific photoproducts were annealed to a complementary uracil-containing (+) strand that contained one or more unique pairs of nucleotide mismatches and used to prime (-) strand synthesis with a DNA polymerase and dNTPs. Following DNA synthesis, the reaction mixtures were incubated with T4 DNA ligase and ATP and then used to transfect SOS-induced competent CSRO6F' cells (uvrA6 and phr-1). The transfectants were plated, gridded, and probed by oligonucleotides specific for progeny of the (-) and (+) strands. Individual progeny of the photoproduct-containing (-) strands were plaque purified and sequenced by the dideoxy method. The cis-syn and trans-syn-I dimers were found not to be very mutagenic (<9%), the Dewar product more so (<33%), and the (6-4) product the most mutagenic (<73%). The mutation spectra were similar to those previously reported for the same photoproducts of the TT site of AGTTGG in the (+) strand of an M13 vector [Lawrence, C. W., et al. (1990) Mol. Gen Genet. 222, 166-168; LeClerc, J. E., et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 9685-9689] except that -1 deletion mutations were not observed for the trans-syn-I photoproducts, and a lower frequency of 3'-T-->C mutations was observed for the (6-4) photoproduct. Evidence that a small percentage of (+) strand repair of a double mismatch to the 3'-side of the photoproduct. Evidence that a small percentage of (+) strand repair of a double mismatch to the 3'-side was obtained from transfection experiments in which a second double mismatch was introduced opposite or flanking the photoproduct. Analysis of the minor tandem mutations induced by the (6-4) and Dewar products suggests that the SOS polymerase complex is able to elongate what amounts to double mismatches opposite these photoproducts and is consistent with the action of a highly processive polymerase that lacks proofreading ability.

Collaborative practice within the intensive care unit: a deconstruction

The concept of collaborative practice has attracted much attention in the last few years--how well do doctors and nurses work together as a team in providing the best possible care for their patients? Consequently there are numerous articles on the subject, most of which seem to suggest that collaborative practice is essential, particularly within the intensive care unit (ICU). It has been linked to both job satisfaction and to patient outcomes (mortality or readmission to the ICU). Indeed, it seems to have evolved as a benchmark for good ICU practice. This paper focuses on some of the most influential writings on this phenomenon, the first stage of a postgraduate study on collaborative practice in intensive care. A deconstructive reading of such literature raises some interesting questions. There are inadequacies in the existing claims, which perhaps suggest that a re-examination of both the feasibility and desirability of collaborative practice is needed.

Latex allergy. Review of 44 cases including outcome and frequent association with allergic hand eczema

BACKGROUND AND DESIGN

Latex allergy is a type I reaction to natural rubber latex (NRL) proteins with clinical manifestations ranging from contact urticaria to fatal anaphylaxis. Previous US studies on NRL allergy have largely been reported by allergists with little detailed information on concomitant hand eczema, contact allergy, or on outcome. The charts of all patients with latex allergy seen between 1980 and 1994 in a dermatology department are reported with results of history; prick, scratch, wear, and patch tests; latex radioallergosorbent test; and follow-up questionnaire.

RESULTS

There were 44 patients (37 female) with NRL allergy; 34 of whom had atopy. In 38 it was occupationally related, with all but two in health-related professions. Of the six nonoccupational cases, three had spina bifida. Twenty-nine had local skin reactions of urticaria and/or pruritus; seven, anaphylaxis; and eight, contact urticaria with other systemic symptoms. The diagnosis was based on a positive prick or scratch test to NRL in 37 cases, a class 2 or greater latex radioallergosorbent test in five cases, and strongly positive wear test results to an NRL glove in two cases. Thirty-six patients had hand eczema, with 26 having relevant positive patch test results that included glutaraldehyde, latex and vinyl gloves, and rubber chemicals. Follow-up revealed one patient quit work and eight changed jobs or tasks because of NRL allergy, 33 of 39 continued to have symptoms at work, and 12 had lost work time because of latex allergy symptoms.

CONCLUSIONS

Latex allergy was frequently seen in health care or dental workers, which was frequently associated with systemic symptoms, hand eczema, and allergic contact dermatitis. Most continue to work, but remained symptomatic. Patients with NRL allergy should be provided information on nonlatex devices and latex avoidance in medical, dental, and occupational settings. Low-NRL allergen gloves should be worn by coworkers of health care workers with NRL allergy.

Purification and partial characterization of (6-4) photoproduct DNA photolyase from Xenopus laevis

The (6-4) photoproduct DNA photolyase was detected in two vertebrate animals Crotalus atrox (rattlesnake) and Xenopus laevis (South African clawed toad). The enzyme was extensively purified from X. laevis and characterized. The highly purified enzyme is fluorescent with an excitation maximum at 420-440 nm and emission maximum at 460-480 nm. The photorepair action spectrum matches the fluorescence excitation spectrum with a 430 nm maximum.

Latex hypersensitivity: its prevalence among dental professionals

Reports of hypersensitivity to latex are growing among oral health care workers, who have a high degree of exposure to latex products. The authors undertook a study to determine the prevalence of latex hypersensitivity among oral health care workers in a hospital dental practice. Among the 34 people who participated in the study, 12 percent had positive results in a skin prick test for latex. This suggests that the true prevalence rate of immediate hypersensitivity to latex in this group of oral health care workers is similar to that in other health care workers who use latex gloves frequently.

Statistical error mapping for reliable quantitative T1 imaging

We developed a statistically based error image for rapid appreciation of unreliable regions in quantitative water proton T1 images. The chi-squared error and co-efficient of variation of the fitted parameter were used to estimate uncertainties in the goodness-of-fit to mono-exponential T1 relaxation and the reliability of the calculated T1, respectively, for each pixel. Errors exceeding a statistical threshold based on a .1 acceptance criterion were displayed as a color-coded overlay on the T1 image. Error maps of quantitative T1 images from 31 healthy volunteers showed a characteristic error structure; few pixels within the parenchyma had excessive errors. Clinical cases with stroke and sickle cell disease showed deviations from the normal pattern in the spatial distribution and magnitude of chi-squared errors. Disease states may deviate from mono-exponential T1 relaxation more than normal brain does. The color-coded error map is a valuable tool for investigators using quantitative MR imaging to determine tissue relaxation parameters.

Visualization of surface figure by the use of Zernike polynomials

Commercial software in modern interferometers used in optical testing frequently fit the wave-front or surface-figure error to Zernike polynomials; typically 37 coefficients are provided. We provide visual representations of these data in a form that may help optical fabricators decide how to improve their process or how to optimize system assembly.

Conformational modeling of substrate binding to endocellulase E2 from Thermomonospora fusca

Molecular mechanics calculations have been used to place a cellotetraose substrate into the active site of the crystallographically determined structure of endocellulase E2 from Thermomonospora fusca. In the lowest energy model structure, the second residue of the substrate oligosaccharide is tilted away from the planar ribbon geometry of cellulose as it is in the X-ray structure of the E2cd-cellobiose co-crystal. This tilt is the result of the topology of the binding site, and results in several strong carbohydrate-protein hydrogen bonds. The tilting produces a twisting of the glycosidic linkage of the cleavage site between residues two and three. In the predicted enzyme-substrate complex both of the Asp residues believed to function in general acid and base roles in the previously proposed model for the mechanism are distant from the bond being cleaved. Molecular dynamics simulations of the complex were conducted, and while the putative catalytic Asp residues remained distant from the cleavage site, the proton of Tyr73 briefly came within van der Waals contact of the linkage oxygen.

Allergy to Unna boots in four patients

We report the cases of four patients seen in our department since 1967 with allergic reactions to preservatives in Unna boots. The first three patients had reactions to parabens and the last had a photoallergic reaction to hexachlorophene. Preservative-free Unna boots were successfully applied to patients with allergy to parabens. A table of some currently available Unna boots, detailing their ingredients, is also presented.

Dynamic contrast-enhanced MR imaging evaluation of osteosarcoma response to neoadjuvant chemotherapy

Assessment of osteosarcoma response to neoadjuvant chemotherapy has prognostic implications, but conventional imaging techniques have been unable to provide an accurate quantitative measure of tumor response. We developed an analysis of dynamic contrast-enhanced MR imaging (DEMRI) to render an image of dynamic vector magnitudes (DVM) and to summarize the result in a quantitative parameter, mean DVM for the lesion (mu DVM). We compared the mu DVM from the examination before surgery with histologic results from an en bloc resection of the tumor in 19 cases. The final mu DVM value provided an accurate (89.5%) measure of tumor necrosis in osteosarcoma. Further, we analyzed the findings in 17 patients with osteosarcoma who completed three DEMRI examinations during the course of therapy. Tumors with higher mu DVM values at presentation had greater decreases in the parameter over the course of therapy. These results are consistent with the distribution of DVM values in these lesions serving as an indicator of tumor perfusion and a possible surrogate variable for drug delivery.

A critical period for axon regrowth through a lesion in the developing mammalian retina

Although the central nervous system of mature mammals is incapable of regeneration, certain elements present in the developing system must permit and promote the growth of new axons to their initial targets. We investigate whether the environment of a developing visual system is capable of supporting regeneration in the Brazilian opossum Monodelphis domestica, in which the retinofugal system develops postnatally. Retinae were lesioned up to the 16th postnatal day and analysed for regeneration after a further 7-10 days. Anterograde tracing with Dil showed axons to have regrown from the axotomized area of retina directly through the lesion. Retrograde tracing with horseradish peroxidase injected into the superior colliculus confirmed that axons from the lesioned area of retina had grown to an appropriate position in the midbrain. The proportion of retinae in which axonal continuity was restored across the lesion decreased as the visual system matured, falling to zero after the 12th postnatal day. Thus a critical period exists in the postnatal opossum in which a retinal lesion permits axon passage. Correlating these results to the known pattern of retinofugal pathway development provides an insight into factors that may restrict this critical period to the 12th postnatal day, and suggests that at least some of the axotomized neurons are regenerating.

Neurolaw: towards a new medical jurisprudence

Traumatic brain injuries and spinal cord injuries occur in a variety of accidents which may become the subject of civil litigation. A new field of medical jurisprudence, called neurolaw, is emerging to join health-care professionals and attorneys in a common quest to employ legal remedies to enhance the quality of life for individuals with neurological injury and their families. Presented here is a review of the underpinnings of this developing area of inquiry.

Developmental determinants at the mammalian optic chiasm

The mammalian optic chiasm is widely and properly regarded as a region where axons from the temporal retina take an uncrossed course and separate from axons arising in the nasal retina that take a crossed course. However, this is but a rough approximation of the adult situation, and developmental studies must take account of several distinctive stages and axon rearrangements that characterize the region of the chiasm. At the early and late stages of development of nonprimate species the axons do not segregate in accordance with a strict naso-temporal rule at all, and their behavior at the chiasm is not relevant to the formation of the naso-temporal division. As the axons pass from the eye to the chiasm they tend to lose their retinotopic order, to gain a chronotopic order, and then, in the region of the chiasm, to regain some aspects of the retinotopic order before reaching their terminal sites. Molecular or cellular cues that allow the several distinct organizational steps to occur must be expected in the retina, on the axons themselves, and also along the pathway of the axons, prechiasmatically and at the chiasm. Some of these cues will be associated with local nerve cells, some with specialized glial elements and some with the retinofugal axons themselves. Several candidate molecules have been identified in the retina and along the path of the axons, but to date no clearly defined role in the specific events of the pathway determination have been identified. The sequence of developmental processes that characterizes the formation of the optic chiasm provides an interesting and useful challenge to experimentalists, because the advancing axons can now be observed in vitro and in the living brain. The pattern of growth changes as development proceeds, it shows distinctive properties in different species and in their genetic mutants, and it can be readily modified by simple experimental procedures. These all provide opportunities for investigating the function of proposed molecular cues that act in the development of the chiasm.

Effect of a very early monocular enucleation upon the development of the uncrossed retinofugal pathway in ferrets

Monocular enucleations were done in ferret embryos before or during the earliest stages of development of the retinofugal pathway (E23-E26). The effects on the development of the uncrossed pathway from the surviving eye were assessed on embryonic day 30. This stage was chosen for two reasons: (1) we show that in normal development a substantial uncrossed component from the temporal crescent has developed by E30; and (2) the pathway cannot yet have been affected by the cell death that normally occurs in the retina in the perinatal period. Using DiI labelling from either the temporal crescent or the optic nerve head, we have shown that such early enucleations prevent the formation of the uncrossed pathway from the temporal crescent of the surviving eye. Enucleation at E23/24, before or during the period when the first axons reach the chiasm, prevents the formation of the uncrossed projection. The axons that would normally take an uncrossed course stall lateral to the midline of the optic chiasm. At E26, when many axons have reached the optic chiasm, but none yet come from the temporal crescent, enucleation causes a dramatic reduction in the uncrossed projection, and the complete abolition of the normal uncrossed pathway from the temporal crescent. This demonstrates that there is a requirement for an interaction between the axons of the two eyes at the optic chiasm to establish the normal formation of the uncrossed pathway at the optic chiasm.

Early development of efferent projections from the chick tectum

The early development of the uncrossed tectobulbar and the crossed tectospinal tracts was studied. These two projections arise from the same structure, the mesencephalon, and develop during the same time period, but follow divergent courses. We have traced the pathways followed by these projections and identified the positions at which axon guidance decisions are made. The first neurons differentiate either side of the entire rostrocaudal extent of the dorsal midline and initiate axons that extend dorsoventrally across the surface of the tectum. At the ventral edge of the tectum these axons turn abruptly and fasciculate to form a caudal descending projection to the hindbrain. These axons extend to the caudal hindbrain and do not project to the periphery along cranial nerve roots. We therefore consider this tract to be the tectobular, rather than the mesencephalic division of the trigeminal. While the tectobulbar projection is still developing, a second wave of axons is initiated, which arises from only the rostral part of the tectum. These axons grow beyond the tectobulbar turn point and continue toward the ventral midline, where they cross the floor plate, before turning caudally at the lateral edge of the main descending hindbrain tract, the ventrolateral tract. We discuss the development of these tracts with reference to possible guidance cues mediating their course.

Does early monocular enucleation in a marsupial affect the surviving uncrossed retinofugal pathway?

Monocular enucleations have been done during early stages (postnatal days 3 to 9) of visual system development of Monodelphis domestica, in order to determine whether in this marsupial, as in several eutherian mammals, there are any interactions between the pathways from the two eyes in establishing the uncrossed retinofugal projection. We have examined the distribution and the number of retrogradely labelled ganglion cells that project to the same side of the brain from the surviving eyes shortly after the uncrossed pathway is first formed in normal development (postnatal days 14 to 28). Even at these early stages of development the surviving uncrossed pathway shows no significant reduction, confirming earlier observations of adult marsupials and showing that at no stage in development is there any evidence that the crossed pathway from one eye influences the navigation of axons that will form the uncrossed pathway from the other eye. This is in sharp contrast to observations of mice, rats and ferrets and is in accord with expectations based on the difference of the chiasmatic structure in marsupials as compared with eutherians.

An innovative approach to respiratory management for long-term care patients

Chronic obstructive pulmonary disease (COPD) is a condition that incapacitates a person physically, psychologically, and socially. Most of the supportive literature of respiratory care programs addresses noninstitutionalized patients. Many long-term care patients have relinquished much of their responsibility for self-care and health promotion. Patients often lack knowledge of the meaning of their disease, the role of exercise, nutrition, smoking, and medication. These factors, coupled with long-term institutionalization, contribute to progressively increasing disability. Our COPD program builds on the concepts of enablement and excess disability. A multidisciplinary team provides patients with the "tools" that allow them to take active responsibility for their health.

T4 endonuclease V protects the DNA strand opposite a thymine dimer from cleavage by the footprinting reagents DNase I and 1,10-phenanthroline-copper

The glycosylase/abasic lyase T4 endonuclease V initiates the repair of ultraviolet light-induced pyrimidine dimers. This enzyme forms an imino intermediate between its N-terminal alpha-NH2 group and C-1' of the 5'-residue within the dimer. Sodium borohydride was used to covalently trap endonuclease V to a 49-base pair oligodeoxynucleotide containing a site-specific cyclobutane thymine dimer. The bound and free oligonucleotides were then subjected to nuclease protection assays using DNase I and a complex of 1,10-phenanthroline-copper. There was a large region of protection from both nucleases produced by endonuclease V evident on the strand opposite and asymmetrically opposed to the dimer. Little protection was seen on the dimer-containing strand. The existence of a footprint with the 1,10-phenanthroline-copper cleavage agent indicated that endonuclease V was interacting with the DNA predominantly via the minor groove. Methylation by dimethyl sulfate yielded no areas of protection when endonuclease V was covalently attached to the DNA, indicating that the protein may closely approach the DNA without direct contact with the bases near the thymine dimer. The Escherichia coli proteins Fpg and photolyase display a very different pattern of nuclease protection on their respective substrates, implying that endonuclease V recognizes pyrimidine dimers by a novel mechanism.

Generalized non-Langerhans cell histiocytosis: four cases illustrate a spectrum of disease

BACKGROUND

The proliferation of non-Langerhans cell histiocytes is a poorly understood process of unknown cause. Variation in the clinical features and/or histopathology of histiocytic proliferation has led to subclassification of the general category of non-Langerhans cell histiocytes. Although the current classification may provide some useful generalizations in regard to the anticipated clinical course, wide variability in presentation and outcome make this classification less than optimal when dealing with individual patients. The objectives of the study were to present four cases of generalized non-Langerhans cell histiocytosis.

MATERIALS AND METHODS

Medical records and slides of four patients diagnosed with non-Langerhans cell histiocytosis at the Cleveland Clinic are reviewed.

RESULTS

The patients exhibit features of more than one subtype of non-Langerhans cell histiocytosis.

CONCLUSION

The overlap among the clinical and histologic features of the generalized cutaneous non-Langerhans cell histiocytic disorders suggests that they represent one disease entity with a wide spectrum of presentations rather than many distinct disorders.

Rescue of motoneuron and muscle afferent function in cats by regeneration into skin. II. Ia-motoneuron synapse

1. In this study we describe application of high-frequency stimulation to the group Ia afferent-to-motoneuron synapse of cats to determine the extent to which regeneration of axotomized muscle afferents and motoneurons into skin or into muscle rescues their ability to generate excitatory postsynaptic potentials (EPSPs). 2. The medial gastrocnemius (MG) muscle nerve was transected and 1) left chronically axotomized, 2) cross-united to the caudal cutaneous sural (CCS) nerve, or 3) self-united. The ability of the operated MG muscle afferents to generate EPSPs in normal lateral gastrocnemius-soleus (LGS) motoneurons and of normal LGS muscle afferents to generate EPSPs in the operated MG motoneurons was tested 5 wk-30 mo later. 3. EPSPs were generated by bursts of 32 shocks at 167 Hz and averaged in register. In normal cats, EPSP amplitude decreased (negative modulation) during these bursts in type S motoneurons and could increase or decrease in type F motoneurons (positive or negative modulation). 4. After axotomy, EPSPs generated both in axotomized motoneurons and by axotomized afferents showed only negative modulation during the burst, and the negative modulation was much greater than in normal animals. Regeneration of the muscle nerve into skin significantly decreased the negative modulation relative to axotomy. Regeneration of the muscle nerve into muscle restored the EPSP modulation behaviors even more, to essentially normal values. 5. We conclude that the ability of muscle afferents to generate EPSPs in motoneurons in response to high-frequency stimulation, and the ability of motoneurons to express those EPSPs, are both influenced by the target innervated by those neurons. Synaptic efficacy is severely reduced by target deprivation (axotomy), partially rescued by cross-regeneration into skin, and rescued virtually completely by regeneration into the native muscle. We speculate on the role of target-derived neurotrophins in these effects.

Rescue of motoneuron and muscle afferent function in cats by regeneration into skin. I. Properties of afferents

1. In this study we investigate the peripheral receptive field properties and spinal cord connections of low-threshold muscle afferent fibers cross-regenerated into the skin to determine whether a cutaneous target can rescue physiological functions lost after chronic axotomy. 2. In adult cats the medial gastrocnemius (MG) muscle nerve was coated with the distal cut end of either the caudal or lateral cutaneous sural nerves and allowed to regenerate into the hairy skin (postoperative period 6-30 mo). During terminal acute experiments we made recordings of single MG afferent fibers in dorsal root filaments and peripheral nerve. Conduction velocity and receptive field characteristics were determined for each fiber. In addition, the MG nerve was stimulated to elicit cord dorsum potentials and monosynaptic excitatory postsynaptic potentials (EPSPs) in heteronymous motoneurons. As controls, studies were carried out after MG nerve axotomy (postoperative period 2.5-12 mo). 3. After innervation of the skin, MG muscle afferent fibers exhibited firing characteristics and proximal segment conduction velocities like those of normal MG afferents. Responses to skin and hair stimulation consisted primarily of slowly adapting, stretch-sensitive, and steady discharge patterns, all common in normal muscle afferents but not in cutaneous afferents. These properties were observed despite the innervation of touch domes and single hairs, suggesting that the peripheral physiology of muscle afferents is a function of the axonal membrane and is not respecified by a cutaneous target and/or receptors. 4. Cord dorsum potentials were characteristic of those elicited by intact muscle afferents rather than skin afferents and showed recovery of configurations lost after chronic axotomy. 5. The monosynaptic EPSPs elicited in lateral gastrocnemius-soleus motoneurons also recovered from the reduction in amplitude observed after chronic axotomy. The configurations of these EPSPs were characteristic of muscle afferents rather than skin afferents. 6. These experiments demonstrate that the peripheral and central physiological properties of muscle afferents are rescued from the axotomy state if the afferents are allowed to reinnervate skin. We found no evidence that respecification had occurred to bring the function of muscle afferents into accord with the new cutaneous target.

Preparation and characterization of a deoxyoligonucleotide 49-mer containing a site-specific thymidylyl-(3',5')-deoxyadenosine photoproduct

Irradiation of d(GTATTATG) with 254 nm light gave rise to four major photoproducts, two of which were readily identified by NMR as the cis-syn cyclobutane dimer and the (6-4) photoproduct of the central TT site. Analysis of the NMR data for the other two photoproducts indicated that they were not any of the other known photoproducts of a TT site and might be TA* photoproducts [Bose, S. N., et al. (1983) Science 220, 723-725]. In support of this possibility, the fluorescence spectra of the products of acid hydrolysis of the two photoproducts were very similar to that reported for the hydrolysis product of the TA* photoproduct of TpdA. Only one of the two TA*-containing octamers could be ligated at both ends to form a 49-mer oligonucleotide in the presence of a complementary oligonucleotide scaffold, suggesting that the TA* photoproduct had formed between T5 and A6. The position of the TA* photoproduct was confirmed by mapping the arrest sites for 3'-->5' exonucleolytic degradation of the 49-mer by T4 DNA polymerase and for primer extension opposite the 49-mer by exonuclease deficient Klenow fragment (KF) and Sequenase Version 2.0. The TA* product could also be bypassed by both polymerases, but it was less of a block to KF. Treatment with 1 M aqueous piperidine at 100 degrees C led to a maximum of about 34% cleavage of the DNA at the site of the TA* product.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-related changes in proton T1 values of normal human brain

To determine whether there were age-related changes in the brain tissue of 55 healthy adult volunteers (29 men, 26 women; 18-72 years old) without known brain abnormalities, a standard inversion-recovery technique was optimized for precise and accurate T1 measurement within the constraints of a 15-minute examination. Measurements of water proton T1 were obtained in eight brain regions. T1 increased with age in the genu (P < .001) (analysis of variance), frontal white matter (P < .05), occipital white matter (P < .05), putamen (P < .001), and thalamus (P << .001). A significant decrease in T1 with age was found in cortical gray matter (P < .05). Thus, age-related changes in T1 are present in a healthy population, even if extremes of age are excluded, suggesting that T1 values generally increase with age. However, increases in T1 were also observed in the genu, putamen, and thalamus of a substantial fraction of volunteers less than 35 years old. Aging healthy persons can show subtle, nonsymptomatic brain changes, suggesting that brain aging is associated with occult processes that can begin at a relatively early age.

Managing latex allergies in the dental office

The consequences of latex allergy can be serious. This paper details the types of allergic reactions and management strategies for both dental workers and patients.

Early development of the optic chiasm in the gray short-tailed opossum, Monodelphis domestica

We have studied the early development of the uncrossed retinofugal projection in the gray short-tailed opossum. Axons that form the adult uncrossed retinofugal projection arise from the temporal crescent of the retina and reach the optic chiasm on postnatal day 7. The sites at which the uncrossed fibres segregate from the crossed fibres and the pattern of this segregation are very different from those seen in eutherian mammals. In the opossum, the uncrossed fibres segregate from the crossed fibres within the juxtachiasmatic part of the optic nerve before they have encountered either the fibres of the other eye or midline structures of the ventral diencephalon. The uncrossed fibres turn perpendicular to the axis of the nerve and grow dorsoventrally through the crossed projection to gather as a discrete bundle at the ventral edge of the nerve. The abrupt divergence of the uncrossed fibres occurs at a border between two glial cell types: the interfascicular glia that characterise the main part of the optic nerve and the radial glia of the juxtachiasmatic part of the nerve. At the ventral part of the nerve, the bundle of uncrossed fibres turns caudally across the axis of the nerve and enters the ipsilateral optic tract. When retinofugal fibres encounter the border between the interfascicular and radial glia, a very specific axonal reorganisation occurs in marsupials, and this is strikingly different from the axonal reorganisation that occurs at the same site in eutherians, where essentially all retinofugal fibres reorganise, not just the uncrossed component. We believe this to be an important example of an identified cellular element that has quite distinct axon-guidance properties in different species.

Malpractice implications of pressure ulcers

This article explores the legal ramifications flowing from the negligent treatment of pressure ulcers. A review of litigated cases provides examples of how American courts deal with this complex condition. References that may be used to reduce vulnerability to malpractice claims are provided.

Precise and accurate measurement of proton T1 in human brain in vivo: validation and preliminary clinical application

Precise and accurate inversion-recovery (PAIR) magnetic resonance (MR) measurements of T1 were obtained in eight brain regions and cerebrospinal fluid of 26 healthy volunteers. Accuracy of the technique was assessed by measuring T1 in small fluid volumes with the PAIR technique and with two independent spectroscopic techniques. The mean difference between T1 measured with PAIR and with the two spectroscopic techniques was 3.1% +/- 1.3. The precision (reproducibility) of measurements with the PAIR technique was excellent. The coefficient of variation (CV) across 16 measurements in a head phantom was 2.0%, compared with a CV of 2.7% across 45 separate measurements in a single subject. The within-subject CV was 1.8% +/- 0.6 in white matter and 1.4% +/- 1.0 in basal ganglia. The between-subject CV in 26 healthy volunteers was 3.6% +/- 0.6 in white matter and 4.1% +/- 1.9 in basal ganglia. Comparison between a patient with an active recurrent brain tumor and an age-matched patient with an inactive brain tumor showed that T1 was significantly elevated throughout the brain of the active-tumor patient, especially in white matter tracts, even though no tumor or edema was detected in the white matter on standard MR images. Comparisons between five brain tumor patients and four healthy volunteers of similar age showed that T1 was significantly and substantially elevated throughout the white matter tracts and in the caudate nucleus, putamen, and thalamus. These results are consistent with the hypothesis that white matter tracts are selectively vulnerable to edema and that T1 increases in white matter are a sensitive indicator of patient status or tumor aggressiveness.

Transcript cleavage by RNA polymerase II arrested by a cyclobutane pyrimidine dimer in the DNA template

A current model for transcription-coupled DNA repair is that RNA polymerase, arrested at a DNA lesion, directs the repair machinery to the transcribed strand of an active gene. To help elucidate this role of RNA polymerase, we constructed DNA templates containing the major late promoter of adenovirus and a cyclobutane pyrimidine dimer (CPD) at a specific site. CPDs, the predominant DNA lesions formed by ultraviolet radiation, are good substrates for transcription-coupled repair. A CPD located on the transcribed strand of the template was a strong block to polymerase movement, whereas a CPD located on the nontranscribed strand had no effect on transcription. Furthermore, the arrested polymerase shielded the CPD from recognition by photolyase, a bacterial DNA repair protein. Transcription elongation factor SII (also called TFIIS) facilitates read-through of a variety of transcriptional pause sites by a process in which RNA polymerase II cleaves the nascent transcript before elongation resumes. We show that SII induces nascent transcript cleavage by RNA polymerase II stalled at a CPD. However, this cleavage does not remove the arrested polymerase from the site of the DNA lesion, nor does it facilitate translesional bypass by the polymerase. The arrested ternary complex is stable and competent to resume elongation, demonstrating that neither the polymerase nor the RNA product dissociates from the DNA template.

A new ATP-independent DNA endonuclease from Schizosaccharomyces pombe that recognizes cyclobutane pyrimidine dimers and 6-4 photoproducts

We have discovered a new DNA endonuclease in the fission yeast Schizosaccharomyces pombe which recognizes cyclobutane pyrimidine dimers and (6-4) pyrimidine-pyrimidone photoproducts. S. pombe DNA endonuclease (SPDE) catalyzes a single ATP-independent incision immediately 5' to the UV photoproduct and generates termini containing 3' hydroxyl and 5' phosphoryl groups. Based on these properties, we propose that SPDE may function in a DNA repair capacity, representing the initial recognition/cleavage step of a DNA excision repair pathway.

Discrete signal processing of dynamic contrast-enhanced MR imaging: statistical validation and preliminary clinical application

A high-resolution image-based method was developed to analyze dynamic contrast agent-enhanced magnetic resonance images quantitatively. This method determines the initial rate of contrast agent accumulation, the delayed rate of accumulation, and the maximum enhancement in each pixel. These three parameters allow characterization of the dynamic signal features. Simulated noisy test sets of dynamic enhancement curves have shown this method to yield a fast and accurate characterization of the dynamic signal. Clinical examples of both qualitative image parameter maps and quantitative statistical analysis of the parameter distributions demonstrated the quality and potential of the technique. The technique is designed to yield imaging and quantitative information on contrast agent accumulation that can be useful in detecting residual tumor and evaluating response to therapy, while requiring less than 7 minutes of imaging time and 5 minutes of processing time per study.

WET, a T1- and B1-insensitive water-suppression method for in vivo localized 1H NMR spectroscopy

Suppression of the water signal during 1H magnetic resonance spectroscopy by repeated sequences of a frequency-selective radiofrequency pulse and a gradient dephasing pulse requires nulling of the longitudinal component of the water magnetization and is therefore affected by T1 relaxation, RF-pulse flip angles (which depend on B1), and sequence timing. In in vivo applications, T1 and B1 inhomogeneity within the sample may cause spatially inhomogeneous water suppression. An improved water-suppression technique called WET (water suppression enhanced through T1 effects), developed from a Bloch equation analysis of the longitudinal magnetization over the T1 and B1 ranges of interest, achieves T1- and B1-insensitive suppression with four RF pulses, each having a numerically optimized flip angle. Once flip angles have been optimized for a given sequence, time-consuming flip-angle adjustments during clinical examinations are eliminated. This water-suppression technique was characterized with respect to T1 variations, B1 variations, off-resonance effects, and partial saturation effects and was compared to similar techniques. Effective water suppression has been achieved with this new technique in single-voxel spectroscopy examinations of more than 50 brain tumor patients at 1.5 T.

Characterization of (6-4) photoproduct DNA photolyase

Pyrimidine (6-4) pyrimidone photoproduct is the second most abundant UV photoproduct in DNA. Recently, it was reported that Drosophila melanogaster cell-free extracts restored the biological activity of (6-4) photo-product-containing DNA in a light-dependent reaction (Todo, T., Takemori, H., Ryo, H., Ihara, M., Matsunaga, T., Nikaido, O., Sato, K., and Nomura, T. (1993) Nature 361, 372-374) concomitant with the loss of (6-4) photoproduct antigenic sites and (6-4) photoproduct-caused alkali-labile sites. In the present study we show that the (6-4) photoproduct but not its Dewar isomer is the substrate for the enzyme, that the enzyme has an action spectrum peak at 400 nm, and that the efficiency of repair per incident photon is very low compared with cyclobutane pyrimidine dimer photolyases. Furthermore, we provide evidence that the (6-4) photoproduct photolyase converts the photoproduct to unmodified bases probably through an oxetane intermediate.

Effects of nitrate respiration on expression of the Arc-controlled operons encoding succinate dehydrogenase and flavin-linked L-lactate dehydrogenase

Expression of sdhCDAB (encoding succinate dehydrogenase) and lctD (encoding the flavin-linked L-lactate dehydrogenase) is elevated aerobically and repressed anaerobically in Escherichia coli. The repression is initiated by autophosphorylation of the sensor protein ArcB, followed by phosphoryl group transfer to the regulator ArcA. ArcA-P, a global transcriptional regulator, then prevents sdh and lct expression. The stimulus for ArcB is not O2 deficiency per se. In vitro experiments showed that ArcB phosphorylation is enhanced by pyruvate, D-lactate, acetate, and NADH, the concentrations of which are likely to increase with the lack of an effective exogenous electron sink. In addition to their aerobic function, the two primary dehydrogenases also have roles in anaerobic nitrate respiration. Results presented here indicate that the increase of sdh and lct expression by nitrate depended on its chemical reduction, which in turn diminished the ArcA-P pool. Unexpectedly, a mutation in the fnr gene (encoding a global regulator involved in anaerobic metabolism) also alleviated the anaerobic repressions. Mutations in arcB or arcA were epistatic over that of fnr. Moreover, since this relief was counteracted by pyruvate in the growth medium, Fnr appears to affect formation of stimuli for ArcB. It is possible that Fnr also indirectly affects some of the other members of the arcA modulon, e.g., cyoABCDE (encoding the cytochrome o complex), cydAB (encoding the cytochrome d complex), and sodA (encoding the manganese-dependent superoxide dismutase).

Evaluation of impairment due to work-related skin disease

Evaluation of impairment is an important task for dermatologists who evaluate workers with occupational disease. Familiarity with the American Medical Association's Guides to the Evaluation of Permanent Impairment makes this chore easier. Here, the author discusses the evaluation process and urges readers to familiarize themselves with the Guides.

Automated pixel-by-pixel mapping of dynamic contrast-enhanced MR images for evaluation of osteosarcoma response to chemotherapy: preliminary results

An automated technique for pixel-by-pixel computer mapping of tumor necrosis was developed to improve the accuracy and applicability of dynamic contrast agent-enhanced magnetic resonance (MR) imaging in assessing the response of osteosarcoma to preoperative chemotherapy. The technique was evaluated in nine osteosarcoma patients who underwent MR imaging at diagnosis (n = 7) and after preoperative chemotherapy (n = 9). Sequential FLASH (fast low-angle shot) images of the tumor were obtained in one plane every 15 seconds before and for 3 minutes after gadopentetate dimeglumine injection. A region of interest was selected that included the entire tumor area. Slopes representing percent increase in signal intensity over baseline values per minute were calculated automatically for each pixel and displayed as gray-scale maps of the tumor. Matching histologic maps of each tumor were obtained. Visual region-by-region comparison of the pixel and histologic maps showed a high degree of correlation and the ability of the MR imaging technique to help identify small foci of residual viable tumor.

A discrete group of melanin containing cells are coincident with a major reorganization of retinal ganglion cell axons in the optic nerve of Xenopus

Further investigations into the abrupt reorganization of axons in the proximal optic nerve of the frog Xenopus are presented. This reorganization reverses the radial, age-related organization of the projection. At the site of axon divergence a discrete group of melanin-producing astrocytes occurs, which are coincident with the reorganization. These cells are identified as astrocytes by their ultrastructure, and by staining in vitro with an antibody to glial fibrillary acidic protein. In an attempt to see if this reorganization occurs in the absence of pigmented astrocytes, the periodic albino mutant of Xenopus was examined. In this albino a similar reorganization of the retinal axons occurs in the optic nerve, but there is also a population of pigment-containing astrocytes. Unlike the pigment of retinal pigment epithelium, which is lost during metamorphosis in these albinos, the pigmented astrocytes of the optic nerve retain their pigment throughout life. A second approach, used to provide support for the involvement of these pigmented astrocytes in the reorganization, was to study the development of the projection. In early development there is a period prior to gliogenesis in the optic nerve (Stage 47/48) when no pigmented cells are present. At these early stages of development there is no evidence for a reorganization of the retinal axons in the optic nerve. The possible role of these melanin-containing astrocytes in axon guidance is discussed.

Contact leukoderma associated with the use of hair colors

Four cases of contact leukoderma associated with the application of hair rinses and permanent and semipermanent hair colors are described. To our knowledge, this association has not been previously reported. Although none had evidence of pigment loss in other sites, Koebner-induced vitiligo cannot be excluded. In our cases hair color ingredients seem to have had a selective toxic effect on melanocytes. Further study of pigment loss from hair colors is warranted, especially in animal and in vitro assays. Patch testing with putative depigmenting agents in patients should be done with caution, so as to minimize potential for depigmentation in cosmetically important anatomic sites.

Comparative analysis of binding of human damaged DNA-binding protein (XPE) and Escherichia coli damage recognition protein (UvrA) to the major ultraviolet photoproducts: T[c,s]T, T[t,s]T, T[6-4]T, and T[Dewar]T

Human cells contain a protein that binds to UV-irradiated DNA with high affinity. This protein, the damaged DNA-binding protein (DDB), is absent from some xeroderma pigmentosum complementation group E cell strains; therefore, it has been suggested that it may be the damage recognition subunit of a human excision nuclease complex. However, the identity of the UV photoproduct bound by DDB and the role of this protein in nucleotide excision repair have been controversial. In this study, we used several synthetic DNA substrates, each of which contains one of the major UV photoproducts, and DDB purified to apparent homogeneity to quantify the specific binding of DDB to various photoproducts. For comparison, the binding of the same photoproducts by the Escherichia coli damage recognition protein UvrA, which is known to be a subunit of the E. coli excision nuclease, was also measured. UvrA and DDB each bound with high affinity to T[t,s]T, T[6-4]T, and T[Dewar]T, but only marginally discriminated between an undamaged oligomer and an oligomer with a T[c,s]T. In contrast to these similarities with regard to the binding to UV photoproducts, UvrA bound to another excision repair substrate, the psoralen-thymine monoadduct, with high specificity, whereas DDB was unable to distinguish between psoralen-adducted DNA and undamaged DNA. We conclude that DDB may play a special role in the repair of UV damage, but it cannot be the sole damage recognition subunit of human excision nuclease.

Three overlapping lct genes involved in L-lactate utilization by Escherichia coli

In Escherichia coli, the lct locus at min 80 on the chromosome map is associated with ability to grow on L-lactate and to synthesize a substrate-inducible flavin-linked dehydrogenase. Similar to that of the glpD-encoded aerobic glycerol-3-phosphate dehydrogenase, the level of induced enzyme activity is elevated by aerobiosis. Both of these controls are mediated by the two-component signal transduction system ArcB/ArcA, although sensitivity to the control is much more striking for L-lactate dehydrogenase. This study disclosed that the lct locus contained three overlapping genes in the clockwise order of lctD (encoding a flavin mononucleotide-dependent dehydrogenase), lctR (encoding a putative regulator), and lctP (encoding a permease) on the chromosomal map. These genes, however, are transcribed in the counterclockwise direction. No homology in amino acid sequence was found between aerobic glycerol-3-phosphate dehydrogenase and L-lactate dehydrogenase. A phi (lctD-lac) mutant was inducible by L-lactate but not D-lactate. Although the mutant lost the ability to grow on L-lactate, growth on D-lactate, known to depend on a different enzyme, remained normal.

Different rates of axonal degeneration in the crossed and uncrossed retinofugal pathways of Monodelphis domestica

The uncrossed retinofugal fibres in the marsupial Monodelphis domestica form a separate bundle as they pass through the optic chiasm. The uncrossed fibres segregate from the crossed fibres a short distance before they reach the chiasm, gathering as an essentially exclusive bundle in the ventral part of the optic nerve. This bundle then passes laterally through the optic chiasm and into the optic tract. The distinctive position of the uncrossed fibres has allowed us to recognise that, surprisingly, the uncrossed fibres degenerate more rapidly than the rest. Seven days after a monocular enucleation approximately 60-80% of the fibres of the crossed component in the main part of the optic nerve near the chiasm have a normal cross sectional appearance in electron micrographs whereas less than 20% of the fibres in the uncrossed bundle look normal. The rapid degeneration of the uncrossed fibres cannot be related to any morphological parameter of the axons. Their fibre diameters are mainly medium to thick, lying within the range of axon diameters found in the rest of the nerve. The axon-myelin ratios of the uncrossed fibres are also no different from those of the crossed optic fibres. There are no structural peculiarities identifiable with light or electron microscopical methods in either the axons or in the glia of the uncrossed bundle that might account for the more rapid degeneration. There is evidence that the degenerative change in the main part of the optic nerve progresses from the lesion towards the chiasm, and that for the crossed fibres it may progress slightly faster for the thicker than for the thinner fibres. The degeneration in the uncrossed bundle does not fit any of the rules that have been proposed for relating rate of degeneration to fibre diameter. We conclude that the rate of Wallerian degeneration is determined by factors that yet remain to be defined.

Sperm antibodies in a patient with obstructive azoospermia

An artificial spermatocoele was constructed at the level of the caput epididymis in a patient with obstructive azoospermia. Morphologically normal spermatozoa were harvested but motility and progression were inadequate for intra-uterine insemination or in vitro fertilisation. In addition, there was an antispermatozoal antibody response which transuded back into the reproductive tract and coated spermatozoa with antibody. It is recommended that if harvesting of epididymal spermatozoa is contemplated, the serum should initially be assessed for spermatozoal antibody.