Dedifferentiated human articular chondrocytes exhibited a wide variation in their capacity to proliferate and redifferentiate in an alginate suspension culture system. The greatest extent of proliferation and redifferentiation was seen to be dependent on the formation of clonal populations of chondrocytes and correlated inversely with the initial cell seeding density. Redifferentiating chondrocytes seeded at low density (1 x 10(4) cells/ml alginate) compared with chondrocytes that were seeded at high density (1 x 10(6) cells/ml alginate) showed a nearly 3-fold higher median increase in cell number. a 19-fold greater level of type-II collagen mRNA expression, a 4-fold greater level of aggrecan mRNA expression, and a 6-fold greater level of sulfated glycosaminoglycan deposition at 4 weeks of culture. Matrix molecules from low-density cultures were assembled into chondrocyte-encapsulated, spherical extracellular matrices that were readily visualized in sections from 12-week cultures stained with antibodies against types I and II collagen and aggrecan. Ultrastructural analysis of 12-week low-density cultures confirmed the presence of thin collagen fibrils throughout the matrix.

S_mman Hyperbaric oxygen (HBO) has been proposed to reduce tumour hypoxia by increasing the amount of dissolved oxygen in the plasma. That this actually occurs has not been verified experimentally. This study was performed to explore changes in tumour oxygenation induced by treatment with normobaric and hyperbanrc oxygen and carbogen. R323OAc mammary adenocarcinomas were implanted into Fischer 344 rats. Arterial blood gases. blood pressure and heart rate were monitored. Tumour oxygenation was measured polarographically in five sets of animals. They received either normobaric 100% oxygen, hyperbaric (3 atmospheres, atm) 100% oxygen. normobaric carbogen or hyperbanrc (3 atm) carbogen (HBC) ± bretylium.HBO reduced the mean level of low pO, values (< 5 mmHg) from 0.49 to 0.07 (P = 0.0003) and increased the average median pO2 from 8 mmHg to 55 mmHg (P = 0.001). HBC reduced the level of low pO values from 0.82 to 0.51 (P = 0.002) and increased median pO from 2 mmHg to 6 mmHg (P = 0.05). Normobaric oxygen and carbogen did not change tumour oxygenation significantly. Sympathetic blockade with bretylium before HBC exposure improved oxygenation significantly more than HBC alone (low pO2 0.55-0.17, median pO2 4-17 mmHg). HBO and hyperbaric carbogen improved tumour oxygenation in this model, while normobaric oxygen or carbogen had no effect. Syvmpathetic-mediated vasoconstriction dunrng hyperbaric carbogen caused it to be less effective than HBO. This mechanism also appeared to operate during normobanrc carbogen breathing. (Brady et al.. 1981;Henk, 1986;Dische. 1991). During this penrod, several investigators measured tumour oxygenation with simple polarographic microelectrode systems. They showed that HBO improved tumour oxygenation in animals and humans (Jamieson and van den Brenk, 1963Brenk, , 1965.The effects of carbogen (95% oxygen 5% carbon dioxide) breathing were also studied. There were two reasons for using carbogen: the carbon dioxide component would help to maintain tumour blood flow by counteracting oxygeninduced vasoconstriction and also increase oxygen delivery by shifting the haemoglobin-oxygen dissociation curve to the right (Rojas. 1991). Some studies showed that carbogen breathing improved tumour oxygenation and blood flow while others did not (Kruuv et al.. 1967;Inch et al., 1970). These studies were primarily descriptive in nature and did not explore potential mechanisms that might explain the experimental data.A major limitation of the early polarographic measurement studies was the inability to sample more than a few points in any given tumour. The development of a computercontrolled polarographic device (pO2 histograph. Eppendorf. Hamburg, Germany) has led to a resurgence in the measurement of tumour oxygenation. Rapid in situ measurement of multiple points within a tumour is now possible.

A new high-intensity 192Ir source has recently become commercially available for remote afterloading brachytherapy treatment. The dosimetric characteristics (dose rate constant, radial dose function, and anisotropy function) of this source were experimentally determined through the application of AAPM Task Group 43 recommendations. Complete dosimetric data are presented in this manuscript.

The objective of the present study was to assess the association between type of health insurance coverage and use of diagnostic tests and therapies among patients with AIDS-related Pneumocystis carinii pneumonia (PCP). Fifty-six private, public, and community hospitals in Chicago, Los Angeles, and Miami were selected for the study, and the charts of 890 patients with empirically treated or cytologically confirmed PCP, hospitalized during 1987 to 1990 were retrospectively reviewed. Patients were classified by insurance status: self-pay (n = 56), Medicaid (n = 254), or private insurance, including health maintenance organizations and Medicare (n = 580). Primary outcomes were the use and timing of bronchoscopy, the type and timing of PCP therapy, and in-hospital mortality. The results indicate that Medicaid patients were less likely than privately insured patients to undergo bronchoscopy (relative odds = 0.61; 95% CI = 0.40, 0.93; p = 0.02) or to have their diagnosis of PCP confirmed (relative odds = 0.51; 95% CI = 0.33, 0.77), after adjusting for patient, severity of illness, and hospital characteristics. Medicaid patients were approximately three-fourths more likely than privately insured patients (relative odds = 1.73; 95% CI = 1.01, 2.96; p = 0.04) to die in-hospital, after adjusting for patient, severity of illness, and hospital characteristics. However, with further adjustment for confirmation of PCP, Medicaid patients no longer had a significantly higher likelihood of dying in-hospital. We conclude that Medicaid patients are less likely to receive diagnostic bronchoscopy than privately insured or self-insured patients, more likely to be empirically treated for PCP, and more likely to die in-hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

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