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An animal model has been developed using enucleated porcine eyes to evaluate ocular trauma. The eyes were pressurized to approximately 18 mmHg and mounted in a container with a 10% gelatin mixture. The corneas of sixteen pressurized eyes were impacted by a blunt metal projectile (mass of 2.6 gm, 3.5 gm or 45.5 gm) at velocities of 4.0 to 38.1 m/s. The impacted eyes were evaluated by an ophthalmologist. A numerical classification scheme was used to categorize the severity of the ocular injury. A chi-squared test indicates that the injury level is associated with the kinetic energy (KE) and not the momentum of the projectile. The enucleated eyes began to experience lens dislocations when the KE of the projectile was approximately 0.75 Nm, and retinal injuries when the KE was approximately 1.20 Nm.

Introducing experimental values as restraints into molecular dynamics (MD) simulations to bias the values of particular molecular properties, such as nuclear Overhauser effect intensities or distances, (3)J coupling constants, chemical shifts or crystallographic structure factors, towards experimental values is a widely used structure refinement method. To account for the averaging of experimentally derived quantities inherent in the experimental techniques, time-averaging restraining methods may be used. In the case of structure refinement using (3)J coupling constants from NMR experiments, time-averaging methods previously proposed can suffer from large artificially induced structural fluctuations. A modified time-averaged restraining potential energy function is proposed which overcomes this problem. The different possible approaches are compared using stochastic dynamics simulations of antamanide, a cyclic peptide of ten residues.

Purpose: To evaluate the efficacy and toxicity of intravenous vinorelbine as single-agent chemotherapy in patients with advanced or recurrent squamous cell carcinoma of the cervix., Patients and Methods: Between August 1993 and July 1995, 35 patients with advanced or recurrent squamous cell carcinoma of the cervix were entered onto this study. Patients had received no prior therapeutic chemotherapy. The initial dose of vinorelbine 30 mg/m2 was administered as a weekly intravenous infusion. Subsequent doses were unchanged, reduced, escalated, or omitted according to observed toxicity. Patients were evaluated for response and toxicity using standard Gynecologic Oncology Group (GOG) and World Health Organization criteria, respectively., Results: Thirty-three of 35 patients were assessable for response and 35 of 35 for toxicity. The overall response rate was 18% (one complete response [CR], five partial responses [PR]). The mean response duration was 5.2 months and the median survival from treatment for all patients was 11.0 months. The major toxicity was leukopenia, with 61% of patients who had grade 3 or 4. Gastrointestinal and neurotoxicity were infrequent and mild., Conclusion: Vinorelbine has moderate activity in advanced or recurrent squamous cell carcinoma of the cervix. Further studies of combination regimens with this agent are justified in this patient population.

Objective: To draw together insights from three perspectives (health economics, organizational ecology, and institutional theory) in order to clarify the factors that influence entries of providers into healthcare markets. A model centered on the concept of an organizational field is advanced as the level of analysis best suited to examining the assortment and interdependence of organizational populations and the institutional forces that shape this co-evolution. In particular, the model argues that: (1) different populations of healthcare providers partition fiscal, geographic, and demographic resource environments in order to ameliorate competition and introduce service complementarities; and (2) competitive barriers to entry within populations of providers vary systematically with regulatory regimens., Data Sources: County-level entries of hospitals and home health agencies in the San Francisco Bay Area using data from the American Hospital Association (1945-1991) and California's Office of Statewide Health Planning and Development (1976-1991). Characteristics of the resource environment are derived from the Area Resource File (ARF) and selected government censuses., Methods of Analysis: A comparative design is applied to contrast influences on hospital and home health agency entries during the post-World War II period. Empirical estimates are obtained using Poisson and negative binomial regression models., Results: Hospital and HHA markets are partitioned primarily by the age and education of consumers and, to a lesser extent, by urbanization levels and public funding expenditures. Such resource partitioning allows independent HHAs to exist comfortably in concentrated hospital markets. For both hospitals and HHAs, the barriers to entry once generated by oligopolistic concentration have declined noticeably with the market-oriented reforms of the past 15 years., Conclusion: A field-level perspective demonstrates that characteristics of local resource environments interact with interdependencies of provider populations and broader regulatory regimes to affect significantly the types of provider organizations likely to enter a given healthcare market.

We report two cases of cervical facet joint osteoarthritis associated with radiculopathy. Contrast-enhanced computed tomography showed a halo of enhancing soft tissue surrounding the facet joints and narrowing the neural foramen. Hypertrophic synovial masses were discovered and removed at the time of operation in each case, resulting in relief of the radicular symptoms.

Thirty-five patients with advanced gynecologic malignancies were entered into a phase I study evaluating thio-TEPA in combination with cisplatin (50 mg/m2) intravenously every 4 weeks. Thirty-four patients were evaluable for toxicity and response, and one was evaluable for toxicity only. Median age was 53 years (range 28-72), and performance status less than or equal to 2. Prior treatment included chemotherapy in 21 patients, radiation in 15, hormonal therapy in 3, and immunotherapy in 1. Thio-TEPA was given to three or more patients at each of the following dose levels: 15, 20, 25, 30, 40, 50, and 60 mg/m2. Thio-TEPA's primary toxicity was myelosuppression; at 50 mg/m2, grade 3 or 4 granulocytopenia occurred in 13 of 17 cycles, and grade 3 or 4 thrombocytopenia occurred in 8 of 17 cycles. The maximum tolerated dose (MTD) of thio-TEPA was 40 mg/m2; in 35 cycles at this dose, grade 3 or 4 granulocytopenia occurred in 19, and grade 3 or 4 thrombocytopenia occurred in 10 cycles; median granulocyte nadir was 1100 (range 110 to 3600) and median platelet nadir was 90,000 (range 10,000 to 289,000). Fifteen patients received three or more cycles at one dose level; cumulative myelosuppression was observed in 11. Two cases of partial alopecia occurred at 40 and 60 mg/m2 thio-TEPA. Responses were as follows: complete response, 5; partial response, 7; stable disease, 14; progressive disease, 8. In 16 patients with ovarian cancer (15 of whom had previously received cisplatin), there were 4 complete responses and 5 partial responses (overall response rate of 56%). The thio-TEPA dose recommended in combination with cisplatin (50 mg/m2) in phase II trials is 40 mg/m2. Cumulative hematologic toxicity may occur with this regimen.

Fifty-three orbital lesions of various types were studied by computer tomography to assess the capabilities and limitations of this technique. Although CT scanning in ophthalmology is in its infancy, results showed that it is useful in the investigation of a number of pathological conditions, including congenital anomalies, arteriovenous malformations, bone lesions, trauma, inflammation, granulomas, pseudotumors, epidermoid cysts, and tumors arising in or near the optic nerve, behind the optic bulb, or in the lacrimal region, as well as changes following eye surgery.

The cusp writer is a teaching aid used to facilitate understanding of the correlation between cusp angulation and the various occlusal determinants. Cusp writings represent an on-edge view of mandibular movement occurring in translation and rotation. Cusp writings demonstrate that: (1) the influence of incisal guidance on cusp angulation is almost 60 per cent greater in molars and 100 per cent greater in pre-molars than the influence of the condylar guidance; (2) steepening or flattening by wear, grinding, or reconstructing the lingual contour of the upper canine or other incisal guide teeth by as little as 1 mm. can change the incisal guide angulation from 15 to 25 degrees depending upon the vertical overlap; (3) these changes can create interceptive or deflective occlusal contacts with trauma and pain on the balancing side in the molar and temporomandibular joint areas; and (4) the incisal guidance of denture teeth is inevitably altered when teeth are tilted, uprighted, or turned for esthetics or phonetics. Such changes alter the occlusal function, harmony, and stability of the dentures.

In this research, we examine the relative importance of different structural units in a professional organization, the hospital, as they affect organizational effectiveness. The difficulties of measuring effectiveness in a complex professional organization are discussed, and an adjusted measure of surgical outcome is developed. Data are drawn from a prospective study of over 8,000 surgical patients treated by more than 500 surgeons in 15 hospitals throughout the nation. Two different types of analyses are presented, both indicating that hospital features have more impact on surgical outcomes than do surgeon characteristics. The second analysis assesses the relative importance of specific attributes of the hospital, surgical staff organization, and surgeon characteristics on surgical outcomes.

The dramatic and recent regulatory changes in the hospital industry (e.g., TEFRA , DRG-based reimbursement) have given added impetus to the analytic framework developed here. Regulation will play an increasingly important role in the future of hospitals, affecting not only fiscal operations, but organizational and administrative arrangements as well. The conceptual framework developed in this article will be refined and augmented through empirical research. Healthcare executives will then have a stronger basis for adapting organizationally to changes in their regulatory environments, thereby increasing the effectiveness and survival of their institutions.

This article reports the results of a survey of a nationwide sample of more than 900 surgeons and post-surgical nurses, who were asked to rate the relative complexity and uncertainty of 71 surgical procedures frequently performed in hospitals. Average scores assigned to each surgical procedure by both types of raters are reported and the extent of agreement is assessed across indicator questions and types of raters. A surprisingly high level of agreement was observed. Explanations for the extent of agreement are discussed and uses for these scores are described.

The effect of a greater volume of patients with similar conditions being treated at a hospital on the outcomes achieved is studied using a variety of categories of patients, 15 surgical and 2 medical, and involving 550,000 patients treated in over 1,200 nonfederal United States acute care hospitals. After demonstrating that there are significant differences in the outcomes of patients, taking into account patient health status, the authors examine the impact of being treated in a hospital with a high or low volume of similar patients. Strong and consistent evidence is found that high volume is associated with better outcomes for surgical patients, which supports regionalizing patient care by procedure. Two additional variables, relative difficulty of the procedure and risk level of the patients, are analyzed to determine whether they change the relationship between volume and outcome. Some evidence is found that low-volume hospitals are associated with the poorest outcome for low-risk surgical patients. The evidence for medical patients is weak and mixed. Possible alternative explanations for the observed findings for surgical and medical patients are discussed.

Two cases of giant-cell arteritis with cerebral arteritis are presented. The clinical situation and the suggestive but nonspecific angiographic features make the antemortem diagnosis possible. Greater awareness of this entity will facilitate its diagnosis and the institution of effective steroid therapy.

The effect of a greater volume of patients with similar conditions being treated at a hospital on the outcomes achieved is investigated for almost 500,000 selected surgical and medical patients treated in over 1,200 nonfederal United States hospitals. In Part I the authors found strong and consistent evidence for surgical patients that high volume is associated with better outcome; evidence for medical patients was mixed. In this paper the authors include other hospital variables related both to volume and outcome--hospital size, teaching status, and expenditures--to determine whether they mask the true relationship; still, strong and consistent evidence that greater volume produces better outcome was found for both surgical and medical patients. This relation was significant for low-, medium-, and high-risk patients. Among the hospital variations added, only size was consistently and strongly related to outcome; greater size was associated with poorer outcome after accounting for volume. The potential importance of the findings for reducing deaths and days in hospital on a national level is discussed. The evidence is strongly supportive of the need for policies that would promote greater regionalization of a given service, and not greater size, to obtain better quality outcome for patients treated.

Three arrangements for structuring the work of professional participants in professional organizations are described, contrasted and evaluated. Arguments are illustrated by application to the organization of physicians within hospitals. The primary rationale, the support structures that have fostered its development, the key structural features and the advantages and disadvantages of each arrangement are described. The effect on these arrangements of structures and forces external to any particular professional organization is emphasized.

The findings and diagnostic results in 600 examinations of primary and metastatic intracranial neoplasms performed at one hospital with the EMI scanner are presented and the effectiveness of this method is compared with that of radionuclide imaging, cerebral angiography, and pneumoencephalography. The computed scan proved to be highly reliable in the diagnosis of glioma, cerebral metastases, meningioma, and acoustic neuroma.

Movement of the patient's head during computed tomographic studies with the EMI scanner causes some degradation of the quality of the examination. With sufficient movement, major artifacts appear which may obscure intracranial pathology. A simple method of head fixation, utilizing a dental mold, greatly reduces the incidence of unsatisfactory scans.

Characteristics of hospitals may be useful predictors of the economy, efficiency, and effectiveness of services delivered. But it is difficult to explain the variables of cost and quality among hospitals until differences among patients and outcomes are accounted for. A promising new research approach is explored as a source of information on that most elusive of all measures in service organizations--the outcome experienced by clients.

Seven patients had seizures in association with the use of intravenous contrast media for cranial computed tomography. Caution and close observation are indicated when contrast agents are administered to patients with suspected focal brain disorders that may lower the seizure threshold. Patients with tumors metastatic to the brain appear to be at specially increased risk.

Five subjects slowly inhaled a 200-ml bolus of sulfur hexafluoride (SF6) from residual volume (RV) followed by an O2-Ar mixture to total lung capacity, then exhaled to RV, either slowly or as rapidly as possible. Larger amounts of SF6 and N2 were recovered in fast than in slow exhalations. We calculated the gas volumes of the apical and basal halves of the parenchymal mass as functions of exhaled volume during slow exhalations from 1) the difference between SF6 recovered in slow and fast exhalations and 2) an estimate of the apex-to-base concentration profile of SF6 in the lung after inspiration. The maximal volume difference, where the apex contained 600 ml more gas than the base, occurred when 70% of the vital capacity had been exhaled. The same calculation, but using N2 data, gave unrealistically large volume differences. Apparently SF6 delivered as a bolus results in an apex-to-base gradient that is large relative to intraregional gradients, but dilution of the resident N2 by a non-N2 gas results in sizable intraregional gradients.

A new technique for measuring reflectivity differences between two samples is reported. An electrically driven tuning fork is used to place the two samples alternately in the beam of a reflectometer, and a lock-in amplifier is used for detection of the difference signal. Advantages of this system include short deadtime, vacuum operation, and extremely high Q. The sensitivity is such that changes in reflectivity of the order of 0.001% can be observed.

Over the past 18 months we have encountered 11 cases of symptomatic lumbar synovial cysts. This experience occurred during a period during which some 1,800 lumbar computed tomographic scans were done. The apparent increased incidence of these lesions is most likely due to the increased diagnostic ability made possible by the advent of high-resolution computed tomography and magnetic resonance imaging. This is a report and discussion of our 11 cases with a review of the literature. There is nothing distinctive in the physical findings or in the histories of our patients, but we have found, as have others, that high-resolution computed tomographic scanning and magnetic resonance imaging significantly enhance the diagnosis of such lesions.

Occasionally, patients with small supratentorial intracerebral hemorrhages exhibit the sudden onset of neurologic deficits, followed by rapid improvement during the next several days. We analyzed the computed tomographic (CT) and clinical features of a group of nine such patients, who were drawn from a series of 120 patients with intracerebral hemorrhage. The temporal pattern of illness was similar to that of a cerebral ischemic event, but the correct diagnosis of intracerebral hemorrhage was made on the basis of the CT findings.

Previous studies suggested that tetrodotoxin, a poison from the puffer fish, blocks conduction of nerve and muscle through its rather selective inhibition of the sodium-carrying mechanism. In order to verify this hypothesis, observations have been made of sodium and potassium currents in the lobster giant axons treated with tetrodotoxin by means of the sucrose-gap voltage-clamp technique. Tetrodotoxin at concentrations of 1 x 10(-7) to 5 x 10(-9) gm/ml blocked the action potential but had no effect on the resting potential. Partial or complete recovery might have occurred on washing with normal medium. The increase in sodium conductance normally occurring upon depolarization was very effectively suppressed when the action potential was blocked after tetrodotoxin, while the delayed increase in potassium conductance underwent no change. It is concluded that tetrodotoxin, at very low concentrations, blocks the action potential production through its selective inhibition of the sodium-carrying mechanism while keeping the potassium-carrying mechanism intact.