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Biomedical subjects

M A Callahan

Publications and source records attributed to M A Callahan.

At least 37 records · Page 2Linked to original sources

Surgically mismanaged ptosis associated with double elevator palsy.

The primary goal in mismanaged as well as untreated cases of combined double elevator muscle palsy and ptosis is alleviation of the paretic ocular motor imbalance to correct pseudoptosis, followed, if necessary, by levator resection to correct any residual true ptosis component. The great hypotropia often found in double elevator muscle palsy should be corrected, preferably by a muscle transposition procedure combined, in certain cases, with inferior rectus muscle recession if the inferior rectus muscle has contracted. Only in young patients can these two surgical procedures be safely combined, particularly if it is desirable to decrease the number of general anesthetics that the patient must take. Only after proper management of the paretic strabismus should the levator be resected, because, in certain cases, extraocular muscle surgery will completely abolish the upper lid ptosis.

Adult↗

Mustardé flap lower lid reconstruction after malignancy.

The Mustardé rotational cheek flap has been used to reconstruct the lower eyelids of 55 patients since 1964. Results and complications were well-documented with preoperative and postoperative photographs, and the patients have been followed from one to 14 years with a mean age follow-up of seven years. The most frequent complications were downward contraction and sagging of the flap and ectropion of the lid margin. To prevent them, the zygomatico-cheek flap must be carefully designed, rotated, and sutured as high as possible so that immediately postoperatively, the palpebral fissure is only a narrow slit. The flap's lining should be of nasal septal mucosa and cartilage joined with permanent sutures to the medial and lateral canthal tendons.

Adult↗

"Congenital" hematic cyst of the orbit.

A case of true hematic cyst of the orbit in a 10-year-old girl, apparently resulting from birth trauma, is presented. Ultrasonic and clinical features believed to aid the examiner in correctly diagnosing such a lesion are presented. While apparently unique among reported cases, "congenital" hematic cysts of the orbit undoubtedly occur occasionally and the possibility of this entity should be considered in appropriate circumstances.

Birth Injuries↗

Ultrasonically-aided percutaneous orbital aspiration.

Ultrasonography is the most effective diagnostic modality for locating and delimiting cystic orbital lesions, and may often provide an accurate tissue diagnosis. A case is presented demonstrating the ability of ultrasonography to aid in the percutaneous aspiration of selected orbital cystic lesions.

Adolescent↗

Conjunctival flap.

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Cataract Extraction↗

Correlation between phosphorylated H1 histones and satellite DNAs in Drosophila virilis.

Drosophila virilis DNA contains satellites I, II, and III. D. novamexicana DNA contains satellite I. D. virilis H1 histone contains subfractions a, b, c, d, and e; D. novamexicana H1 contains subfractions a, b, and c. Therefore, satellites II and III might be correlated with H1d and H1e. To test the validity of this correlation, the H1 histones of polytene nuclei, which contain less than 1% satellite DNA, were analyzed. Polytene nuclei of D. virilis contain substantially decreased levels of H1c and H1e and marginally decreased levels of H1d. Polytene nuclei of D. novamexicana contain decreased levels of H1c.H1c is correlated with satellite I (common to D. virilis and D. novamexicana); H1e is correlated with satellites II and III; H1d is not correlated with any satellite DNA, because its level is virtually unchanged in polytene cells lacking detectable amounts of satellite DNA. Alkaline phosphatase digestion of the H1 histones reveals that H1c is the phosphorylated form of H1b and H1e is the phosphorylated form of H1d. Therefore, the under-replication of satellite DNAs is correlated with the decreased phosphorylation of H1 histones. In vitro, D. virilis H1 histones preferentially bind D. virilis DNAs in the progression III greater than II greater than I greater than main band, whereas D. virilis core histones do not preferentially bind any D. virilis DNA. As an extension of these results, we suggest that phosphorylated H1 histones bind D. virilis satellite DNAs in vivo and are involved in the compaction of heterochromatin.

Alkaline Phosphatase↗

Slit-beam ruler.

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Corneal Ulcer↗

Synthetic absorbable suture for strabismus surgery.

Polyglactin 910 (Vicryl), a synthetic absorbable braided suture in 5-0 or 6-0 size, was satisfactory for recession and resection of extraocular muscles. It produced an acute allergic reaction in only one of 89 cases (1.5%) as compared to a 19% reaction when collagen suture of like size was used. Polyglactin 910 suture, when left partially exposed, may be irritating and can cause excessive reaction when used at the conjunctival limbus.

Collagen↗

Role of exposure databases in risk assessment.

Risk assessments have assumed an increasingly important role in the management of risks in this country. The determination of which pollutants or public health issues are to be regulated, the degree and extent of regulation, and the priority assigned to particular problems are all areas of risk assessment that influence the country's $100 billion annual investment in environmental protection. Recent trends in public policy have brought the practice of risk assessment under greater scrutiny. As policy makers increasingly insist that specific numerical risk levels (so-called bright lines) be incorporated into regulatory decisions, the stakes for good risk assessment practice, already high, are raised even further. Enhancing the scientific basis of risk assessments was a major goal of the Workshop on Exposure Databases. In this article, we present the Risk Assessment Work Group's evaluation of the use of exposurerelated databases in risk assessment and the group's recommendations for improvement. The work group's discussion focused on the availability, suitability, and quality of data that underly exposure assessments, a critical component of risk assessment. The work group established a framework for evaluation, based on exposure scenarios typically used in regulatory decisions. The scenarios included examples from Superfund, the Clean Air Act, the Toxic Substances Control Act, and other regulatory programs. These scenarios were used to illustrate current use of exposure data, to highlight gaps in existing data sources, and to discuss how improved exposure information can improve risk assessments. The work group concluded that many of the databases available are designed for purposes that do not meet exposure and risk assessment needs. Substantial gaps exist in measurements of actual human exposure and in the data necessary to model exposures, to characterize distributions of exposure, to identify high-risk groups, and to identify possible environmental inequities in exposure. The work group, on the basis of its findings, made both short-term and longer-term recommendations for improving the collection of exposure data in the future.

Animals↗

Informed decisions about protecting and promoting public health: rationale for a National Human Exposure Assessment Survey.

Accurate and reliable exposure-related information is essential for informed decisions about protecting and promoting public health. The need for more and better data on population exposures to environmental chemicals is discussed, with emphasis on the justification for collecting baseline data on exposure distributions for the general population and for important population subgroups. A rationale is provided for undertaking exposure surveillance in the U.S. population by means of a National Human Exposure Assessment Survey (NHEXAS). The knowledge and understanding generated by NHEXAS will contribute to more informed and more credible decisions in three ways: (1) by establishing a core set of approaches, methods, and data that will significantly advance the field of exposure analysis; (2) by developing a strong and direct connection between science (exposure research and surveillance) and policy (decisions about assessment, management, and communication of health risks); and (3) by creating a connected group of researchers and regulators who share a mutual appreciation and understanding of the value of exposure surveillance for well-reasoned decisions.

Decision Trees↗