The Drosophila gene Medea demonstrates the requirement for different classes of Smads in dpp signaling

Signals from transforming growth factor-beta (TGF-beta) ligands are transmitted within the cell by members of the Smad family, which can be grouped into three classes based on sequence similarities. Our previous identification of both class I and II Smads functioning in a single pathway in C. elegans, raised the issue of whether the requirement for Smads derived from different classes is a general feature of TGF-beta signaling. We report here the identification of a new Drosophila class II Smad, Medea, a close homolog of the human tumor-suppressor gene DPC4. Embryos from germline clones of both Medea and Mad (a class I Smad) are ventralized, as are embryos null for the TGF-beta-like ligand decapentaplegic (dpp). Loss of Medea also blocks dpp signaling during later development, suggesting that Medea, like Mad, is universally required for dpp signaling. Furthermore, we show that the necessity for these two closely related, non-redundant Smads, is due to their different signaling properties - upon activation of the Dpp pathway, Mad is required to actively translocate Medea into the nucleus. These results provide a paradigm for, and distinguish between, the requirement for class I and II Smads in Dpp/BMP signaling.

Quantification of insulin in dried blood spots

A method has been developed in which the concentrations of insulin in dried blood spots on filter paper can be estimated. The technique involves elution of blood from the paper, evaporation, and rehydration in assay buffer. The resuspended samples are then assayed by radioimmunoassay. The ratio of control plasma to control dried blood spot insulin values is used as a conversion factor for unknown samples on paper to express the dried blood spot insulin concentration in plasma equivalents. Intra-assay variability was 14%, and interassay variability was 25%, but the elution conversion factor had a variability of about 40% among individuals. This technique has substantial advantages for field studies, but elevated values should be confirmed by a venous plasma sample measurement in a conventional radioimmunoassay.

Acanthosis nigricans as a risk factor for non-insulin dependent diabetes mellitus

The prevalences of obesity and of non-insulin dependent diabetes mellitus (NIDDM) have increased in the United States population over the past two decades, and thus diabetes prevention has become a major concern of public health agencies such as the National Institutes of Health. Identification of individuals at risk for diabetes is an essential first step in designing and implementing intervention programs. Insulin resistance is the hallmark of the pathophysiology of NIDDM. Subjects with hyperinsulinemia, impaired glucose tolerance, or gestational diabetes are well accepted as being at high risk for diabetes. We propose that the easily identifiable skin lesion, acanthosis nigricans, is common in the major minority groups in the United States and that its presence is a surrogate for laboratory-determined hyperinsulinemia.

Elevated suicide levels associated with legalized gambling

There has been no systematic, large-scale statistical investigation of the link between gambling and suicide, despite the suggestion of such a link from small-scale case studies. This article examines whether gamblers or those associated with them are prone to suicide and whether gaming communities experience atypically high suicide rates. Las Vegas, the premier U.S. gambling setting, displays the highest levels of suicide in the nation, both for residents of Las Vegas and for visitors to that setting. In general, visitors to and residents of major gaming communities experience significantly elevated suicide levels. In Atlantic City, abnormally high suicide levels for visitors and residents appeared only after gambling casinos were opened. The findings do not seem to result merely because gaming settings attract suicidal individuals.

Evolutionary origins of the vertebrate dentition: phylogenetic patterns and developmental evolution

The theory that teeth evolved from dermal denticles linked with the origin of jaws no longer accounts for the diversity of new data emerging from the fossil record. We have reviewed oropharyngeal dental patterns in all fossil groups of early vertebrates to establish the primitive condition, in order to understand the polarity of change. The evolutionary precedence of dermal denticles before teeth now seems less likely; both may be alternative manifestations of a common morphogenetic system. This developmental system involves regulatory changes affecting the odontode, a fundamental exoskeletal unit, and can explain skeletal diversity. However, tooth and denticle differences may have diverged at loci deep within vertebrate phylogeny, as real differences exist between them. Teeth were conceived as evolving from non-growing odontodes with regulation of precise increase in size, position, sequence of time of development, and polarity of shape. A characteristic feature of teeth is the ability to replace from a developing sequence, programmed with these parameters, prior to demand. Tooth whorls, a feature of denticles in the oropharyngeal region, may be regarded as a preadaptation of this tooth replacement mechanism. The new fossil evidence suggests that teeth may have evolved from these more specialised oropharyngeal denticles in agnathan vertebrates.

Measurement of airborne flour exposure with a monoclonal antibody-based immunoassay

BACKGROUND

The development of simple and standardised methods to measure airborne levels of workplace biological allergens is an important step in reducing the incidence of occupational asthma. Such a method would be useful for measuring wheat flour allergens which cause asthma in bakers. Measurement of allergen per se rather than total dust enables exposure to be better defined.

METHODS

Monoclonal antibodies were produced, their specificity analysed by immunoblotting and then used to affinity-purify a putative flour allergen. The importance of this protein as an allergen was tested by RAST using sera from allergic bakers and it was identified by N-terminal sequencing. Suitable monoclonal antibodies were chosen to develop an enzyme-linked immunosorbent assay. Commercial baking flours and personal airborne dust samples were analysed using the immunoassay.

RESULTS

A sensitive and specific monoclonal antibody-based enzyme-linked immunosorbent assay was developed to measure a wheat alpha-amylase inhibitor. The wheat alpha-amylase inhibitor content of bulk wheat flours was 0.124% (95% confidence limits 0.083-0.164%) and airborne levels in bakeries had a geometric mean of 744 ng/m3 (95% confidence limits 371-1,496 ng/m3).

CONCLUSION

This assay is suitable for widespread use as the monoclonal antibodies and standards are well defined and potentially infinitely available. The assay therefore offers distinct advantages over those exposure assessment methods currently in use. Comparable results would be obtained by different investigators over a prolonged time period. The assessment of flour allergen exposure and the relationship with clinical response could then be investigated using a multi-centered approach.

Neural crest potential for tooth development in a urodele amphibian: developmental and evolutionary significance

Tooth development in urodele amphibians occurs from a restricted region of anterior cranial neural crest. An in vitro culture system was used to test the odontogenic potential of more caudal regions of neural crest, including an "intermediate region" of neural folds which has never previously been tested for either fate or potential. Explants of different axial levels of neural crest with stomodaeal ectoderm and endoderm demonstrated that odontogenic potential extends not only further caudally than the axial level fated to produce teeth, but also beyond that with potential to produce cartilage. Our results show that chondrogenic potential is found only within the most rostral portion of the intermediate region, but that odontogenic potential extends to its most caudal limit. This separation of skeletogenic cell lineages in the neural crest necessitates a reevaluation of the designations of "cranial" and "trunk" and a reconsideration of the evolutionary implications of developmentally distinct crest-derived mesenchyme populations. The proposal that odontogenic potential extends into the trunk neural crest may be explained as conserved from a phylogenetically older, more extensive skeletogenic ability which produced the exoskeleton of more basal vertebrates.

Histone octamer function in vivo: mutations in the dimer-tetramer interfaces disrupt both gene activation and repression

Within the core histone octamer each histone H4 interacts with each H2A-H2B dimer subunit through two binding surfaces. Tyrosines play a central role in these interactions with H4 tyrosines 72 and 88 contacting one H2A-H2B dimer subunit, and tyrosine 98 contacting the other. To investigate the roles of these interactions in vivo, we made site-directed amino acid substitutions at each of these tyrosine residues. Elimination of either set of interactions is lethal, suggesting that binding of the tetramer to both dimers is essential. Temperature-sensitive mutants were obtained through single amino acid substitutions at each of the tyrosines. The mutants show both strong positive and negative effects on transcription. Positive effects include Spt- and Sin-phenotypes resulting from mutations at each of the three tyrosines. One allele has a strong negative effect on the expression of genes essential for the G1 cell cycle transition. At restrictive temperature, mutant cells fail to express the CLN1, CLN2, SWI4 and SWI6 genes, and have reduced levels of CLN3 mRNA. These results demonstrate the critical role of histone dimer-tetramer interactions in vivo, and define their essential role in the expression of genes regulating G1 cell cycle progression.

[Animal models used for the evaluation of anti-osteoarthritis drugs]

Naturally occurring osteoarthritis occurs in a variety of animal species including mice, guinea pigs, dogs and cynomolgus macaques and some of these animals have been used to evaluate the ability of anti-osteoarthritis drugs to reduce synovial inflammation and preserve cartilage integrity. However, the genetically determined animal models of osteoarthritis require the establishment of colonies which may take several years to develop and may be influenced by the strain of animal used and ill-defined environmental factors. On the other hand, the injection of irritants or enzymes into joints, or destabilization by surgical means, can rapidly and reproducibly lead to joint arthropathy and has therefore been more widely used. Although small animals, particularly rats and rabbits, have been the favoured target species, large animals such as dogs and sheep offer many advantages including the opportunity to undertake topographical analysis of joint cartilage and serial aspiration of synovial fluid. Meniscectomy is a common orthopaedic procedure which, in man and animals, is known to lead to osteoarthritis. In the past we have used this technique to induce osteoarthritis in pure bred dogs but more recently we have employed pure bred Merino sheep, which were matched for age, sex and weight. Using this ovine model we have been able to monitor the early and intermediate stages of cartilage metabolism, as well as identify key proteinases responsible for the loss of proteoglycans from these tissues in osteoarthritis. The effects of anti-osteoarthritis drugs on inflammatory mediators and cartilage metabolism has been successfully studied using the ovine model of osteoarthritis.

Absorption, retention and urinary excretion of chromium-51 in rats pretreated with indomethacin and dosed with dimethylprostaglandin E2, misoprostol or prostacyclin

Drug-nutrient interactions affecting chromium were investigated in this study. Rats were injected with indomethacin to reduce endogenous prostaglandin synthesis and dosed with prostaglandin analogues or prostacyclin. Effects on absorption, tissue distribution and urinary excretion of 51Cr from 51CrCl3 were evaluated using a 2 x 4 factorial experimental design. Forty-eight adult male rats were food deprived for 12 h and then injected intraperitoneally with indomethacin (5 mg/kg body wt) or placebo. Thirty minutes later, rats were intubated and dosed with one of four treatments: a prostaglandin E1 analogue (misoprostol) at 50 microg/kg body wt; a prostaglandin E2 analogue (16,16-dimethylprostaglandin E2) at 7.5 microg/kg body wt; prostacyclin at 20 microg/kg body wt; or control (7.64 mmol/L Tween-80 suspended in 0.15 mol/L NaCl containing 0.48 mol/L ethanol). Immediately after intubation, rats were dosed with 3.7 mBq of 51CrCl3 by micropipette. Blood was collected from the tail at intervals after 51Cr dosing. Six hours after dosing, 51Cr rats were exsanguinated by cardiac puncture. Indomethacin, an inhibitor of prostaglandin synthesis, significantly increased (P < 0.05) 51Cr in blood at all time periods tested except at 15 min. In tissues, indomethacin significantly increased 51Cr retention. Urinary 51Cr excretion at 6 h was higher (P < 0.05) in indomethacin-pretreated rats than in control rats. Administration of indomethacin, which blocks prostaglandin synthesis, enhanced 51Cr absorption, whereas dosing with 16,16-dimethylprostaglandin E2 decreased 51Cr absorption.

Axial pattern flap based on the superficial temporal artery in cats: an experimental study

OBJECTIVE

The purpose of this study was to determine the surgical guidelines for and the survivability of an axial pattern flap based on the superficial temporal artery in cats.

STUDY DESIGN

The mean survival length and mean percentage area of survival of flaps after 7 days in control and experimental groups, are assessed and compared.

ANIMALS

Ten mature, domestic shorthair cats.

METHODS

The superficial temporal artery and vein were incorporated in the flaps of the experimental group (n = 5) and were ligated in the control group (n = 5). Seven days postoperatively, the length of tissue that remained viable in each flap was determined by measurement of the length of the grossly devitalized tissue and subtracting this from total flap length.

RESULTS

Mean width and length of all flaps was 2.0 x 7.0 cm, respectively. Mean survival length (+/- SD) of experimental and control flaps was 6.9 (0.2) cm and 4.4 (2.2) cm, respectively. Necrosis occurred in all control flaps, resulting in a mean percentage area of survival of 62.8 (11.7)%, compared with 98.6 (3.2)% for experimental flaps. Results were significantly different (P < .05) between the experimental and control groups.

CONCLUSIONS

A flap based on the superficial temporal artery may be a source of skin for reconstructive procedures of the maxillofacial region in cats.

CLINICAL RELEVANCE

Knowledge of the anatomic landmarks and survivability of an axial pattern flap are essential considerations when planning a reconstructive technique.

Choristomas of the seventh and eighth cranial nerves

Choristomas, masses of normal tissues in aberrant locations, contain smooth muscle fibers and fibrous tissues. We describe the MR imaging features of two choristomas located in the internal auditory canals and arising from the facial and vestibulocochlear nerves. Both lesions enhanced with contrast material. In one case, enhancement was seen in the geniculate ganglion and greater superficial petrosal nerve. In the other, a medial component enhanced less than the lateral component did.

Hyperactive pectoralis reflex as an indicator of upper cervical spinal cord compression. Report of 15 cases

Myelopathy from cervical spondylosis is often accompanied by hyperreflexia of the upper-extremity deep tendon reflexes (DTRs). Reflexes such as the pectoralis jerk and the deltoid jerk may only be apparent in the context of hyperreflexia. Although the nerve roots involved in the reflex arcs are well described, levels of cervical spinal cord compression that lead to the hyperreflexia are not as clear. This is of particular significance for patients with multilevel cervical spondylosis in determining the levels responsible for their symptoms. The authors examined 15 consecutive patients who presented for treatment of cervical myelopathy. The clinical examination was then correlated with levels of cervical spinal cord compression by cervical magnetic resonance imaging or computerized tomography with intrathecal contrast enhancement. The presence of a prominent pectoralis jerk was seen only in patients with spinal cord compression at the C2-3 and/or C3-4 levels (nine patients). No patient with compression at or below the C4-5 disc space without coexisting compression at a higher level had hyperactive pectoralis reflexes. This association between the C3-4 level and a hyperactive pectoralis reflex was significant (p < 0.004, Fisher's exact test). The deltoid reflex was tested in the last nine consecutive patients. It was present in patients with compression of the upper spinal cord at levels C3-4 and C4-5 (four of five patients) but appeared in only one of four patients with compression below C4-5. This association did not attain statistical significance. The presence of a hyperactive pectoralis reflex is specific for lesions of the upper cervical spinal cord. Examination of upper-extremity DTRs may be helpful in planning the appropriate levels for surgical decompression in patients with multilevel spondylosis and myelopathy.

A Longitudinal Study of Lung Function in Non-asthmatic Workers in an Aluminum Smelter

This paper reports a longitudinal study carried out between 1977 and 1989 to determine whether the long-term rate of change in the forced expiratory volume in 1 second (FEV&inf1;) is influenced by exposure to the potroom environment of an aluminum smelter. Workers with diagnosed asthma were excluded from the analysis. The study population consisted of 393 potroom workers, with rate of change in FEV&inf1; used to assess any impairment in airway function. Post-shift urinary fluoride levels and length of service were used to measure exposure. After allowing for age, smoking behavior, and a standardized measure of FEV&inf1;, the rate of change in FEV&inf1; was found to be significantly greater for those workers who had worked shorter times in the potroom. Possible explanations for this finding include unrecognized asthma, a healthy-worker effect, and an exposure effect that occurs early in a worker's experience in the potroom; these explanations are not necessarily mutually exclusive. Apart from the risk of occupational asthma, there does not appear to be any long-term effect on the rate of decline in FEV&inf1; associated with exposure to the potroom environment in workers who remain at work longer than 40 months.

Influence of the adenovirus 5 E1A oncogene on chromatin remodelling

In the eukaryotic nucleus, compaction of DNA into chromatin can limit the access of trans-acting factors, providing an additional level of regulation to processes such as transcription, replication, and repair. Recent studies have suggested that the protein products of the adenovirus 5 E1A oncogene can influence SWI-SNF and histone acetylase activities, two cellular processes that facilitate transcription in the context of chromatin. This review focuses on the unexpected effects of E1A on cellular processes that remodel chromatin in relation to its transcriptional and transforming activities.

Intravenous access in newborn infants: impact of extended umbilical venous catheter use on requirement for peripheral venous lines

Central venous lines are used to care for critically ill neonates in cases of limited peripheral venous access. This prospective, randomized study evaluated the risks and benefits of the use of single- and double-lumen umbilical venous catheters for up to 14 days. Patients were randomized to one of three treatment arms: (1) single-lumen umbilical catheter, (2) double-lumen umbilical catheter, or (3) no umbilical catheter; peripheral intravenous lines only. Infants in the groups treated with an umbilical venous catheter had significantly fewer venipunctures and peripheral intravenous lines placed during their first 2 weeks of life than those in the peripheral line only group. Less time and money were spent obtaining peripheral line placement in the umbilical venous catheter groups. The incidence rates of sepsis and complications were not higher in treated patients than in control patients. The double-lumen catheter further reduced peripheral venipunctures and lines. We conclude that an umbilical venous catheter used during the first 2 weeks of life is a relatively safe, less stressful, cost-effective means of providing intravenous therapy to neonates.

Chemokine expression in simian immunodeficiency virus-induced AIDS encephalitis

The pathogenesis of neurological dysfunction associated with human immunodeficiency (HIV)-1 infection is uncertain. However, the presence of macrophage infiltrates in the central nervous system is a key feature of HIV encephalitis and is correlated with HIV-associated dementia. Moreover, it has been demonstrated that HIV-infected monocyte/macrophages can produce toxic substances that may play a critical role in the development of HIV-associated dementia. However, the exact mechanisms responsible for HIV infection and leukocyte recruitment to the central nervous system remain speculative. Similar to HIV-infected patients, simian immunodeficiency virus (SIV)-infected macaque monkeys develop immunosuppression and acquired immune deficiency syndrome (AIDS)-related inflammatory disorders, including AIDS encephalitis. In this study, we demonstrate that encephalitic brain from SIV-infected animals has elevated immunohistochemical expression of the C-C chemokines, macrophage inflammatory protein-1 alpha and -beta, RANTES, and monocyte chemotactic protein-3, and the C-X-C chemokine interferon-inducible protein-10. These findings suggest that one or all of of these chemokines could be involved in leukocyte recruitment to the brain in SIV-infected macaque monkeys.

Adenovirus E1A specifically blocks SWI/SNF-dependent transcriptional activation

Expression of the adenovirus E1A243 oncoprotein in Saccharomyces cerevisiae produces a slow-growth phenotype with accumulation of cells in the G1 phase of the cell cycle. This effect is due to the N-terminal and CR1 domains of E1A243, which in rodent cells are involved in triggering cellular transformation and also in binding to the cellular transcriptional coactivator p300. A genetic screen was undertaken to identify genes required for the function of E1A243 in S. cerevisiae. This screen identified SNF12, a gene encoding the 73-kDa subunit of the SWI/SNF transcriptional regulatory complex. Mutation of genes encoding known members of the SWI/SNF complex also led to loss of E1A function, suggesting that the SWI/SNF complex is a target of E1A243. Moreover, expression of E1A in wild-type cells specifically blocked transcriptional activation of the INO1 and SUC2 genes, whose activation pathways are distinct but have a common requirement for the SWI/SNF complex. These data demonstrate a specific functional interaction between E1A and the SWI/SNF complex and suggest that a similar interaction takes place in rodent and human cells.

CT in adult supraglottitis

We describe the CT appearance of supraglottitis and its complications in three adults. The most common CT findings were thickening of the epiglottis, aryepiglottic folds, false and true vocal cords, obliteration of the preepiglottic fa, thickening of the platysma muscle, and reticulation of the subcutaneous fat. Multiple loculated fluid-density collections consistent with abscesses were seen in one patient. Although the diagnosis of supraglottitis is generally made on the basis of the patient's history and by direct endoscopy, CT may be used to confirm the diagnosis when an adequate laryngoscopic examination cannot be performed. CT is also useful in evaluating the complications of this disorder.

Lingual approach for surgical extraction of the mandibular canine tooth in dogs and cats

A lingual approach for surgical extraction of the mandibular canine tooth was developed based on anatomic observations of tissues and structures of the rostral mandible and lingual orientation of the mandibular canine tooth root. Measurements of the lingual and buccal aspects of the alveolus indicated similar quantities of bone required for alveolectomy to expose the tooth root. The surgical procedure was performed in 12 dogs and four cats with no complications reported during the follow-up period.

Repression domain of the yeast global repressor Tup1 interacts directly with histones H3 and H4

Repression of yeast a cell-specific genes by the global repressor Ssn6/Tup1 has been linked to a specific organization of chromatin. We report here that Tup1 directly interacts with the amino-terminal tails of histones H3 and H4, providing a molecular basis for this connection. This interaction appears to be required for Tup1 function because amino-terminal mutations in H3 and H4 that weaken interactions with Tup1 cause derepression of both a cell-specific and DNA damage-inducible genes. Moreover, the Tup1 histone-binding domain coincides with the previously defined Tup1 repression domain. Tup1/histone interactions are negatively influenced by high levels of histone acetylation, suggesting a mechanism whereby the organization of chromatin may be modulated in response to changing environmental signals.