[Radiosensitization of Lewis lung tumor by perfluorochemical emulsion comparison between single and fractionated irradiation]

Previously perfluorochemical emulsion (FDAS) was shown to enhance tumor growth delay, when applied together with breathing carbogen (95% O2+5% CO2) before and during irradiation. In the present paper, radiosensitizing effects of FDAS in tumor bearing mice were examined on a single (10 Gy) and fractionated irradiation (4 Gy, 4 times) and on the dose of administration. The results were as follows; 1) All groups of single irradiation with injection of FDAS 10-40 ml/kg could enhance the radiosensitivity of LLC bearing mice. 2) Tumor growth of even fractionated irradiation groups was significantly delayed by administration of FDAS more than 5 ml/kg. 3) In case of fractionated irradiation, the minimum effective dose of FDAS was estimated to be 5 ml/kg per irradiation, which coincided with that of single irradiation. It was concluded that FDAS in fractionated irradiation could increase the radiosensitivity in tumor bearing mice with more than 5 ml/kg injection. Therefore, FDAS may be useful as a radiosensitizer for clinical application in fractionated radiation therapy. Furthermore, since irradiation doses of single (10 Gy) and even fractionated irradiation (4 Gy X 4 times) were approximately iso effective dose, it may be considered that administration of more than 5 ml/kg (minimum effective dose) FDAS at each irradiation gave similar radiosensitizing effects to both single and fractionated irradiation.

[Use of the carbon dioxide laser in the treatment of leukoplakia]

Experiences obtained in the course of laser surgical treatment of 126 mouth cavity leukoplakias are summarized. The elaborated, differentiated method ensures, besides safe removal of tissues infected by leukoplakia, a possibility for significantly preserving the functions of the mouth cavity. In case of simplex leukoplakia coagulation by means of defocused laser beam of 5 W energy, in case of verrucosus vaporization by means of focused beom of 10 to 15 W, and in erosiv cases excision in carried out by means of focused beom of 20 to 25 W energy. After laser treatment out of 126 patients 118 were free of symptoms. After operation emberging pain, oedema are minimal. (As a rule, the patients are capable of work the other day.) It is stated that the leucoplakias represent one of the most important fields of the oral surgical employment of the CO2 laser beam.

Effect of normobaric oxygen on tumor radiosensitivity: fractionated studies

The sensitizing ability of 100% normobaric oxygen was investigated in a mouse mammary carcinoma (CaNT) using a variety of fractionated regimens. Both regrowth delay and local control were used as assays of tumor response. With both assays, there was a similar and significant increase in radiosensitivity for all fractionated schedules. Enhancement ratios ranged from 1.24 to 1.45, the highest increase being observed with a 30 fraction schedule given in an overall time of 6 weeks. Thus, in CaNT tumors normobaric oxygen is a far more efficient radiosensitizer in fractionated treatments than the oxygen-mimetic compound misonidazole; an oxygen effect being observed at doses per fraction as low as 1.8 Gy. These results suggest strongly that normobaric gases could play an important role in the clinical management of tumors where hypoxia may limit the outcome of radiotherapy.

[Comparison of the effects of carbonated baths with those of carbon dioxide baths, "dry baths"]

Therapeutic activities of CO2 water bathes are explained by a synergism between many factors. The first ones are related to immersion it-self: hydrostatic pressure and Archimedes force inducing orthosympathetic inhibition and muscular relaxation. The second ones depend on the pharmacological properties of carbon dioxide acting directly on the blood vessels of the skin, causing vasodilation and heat sensation. As "dry" carbon dioxide bath is devoid of the physical factors which are necessary for a successful therapeutic activity, such an administration has no interest in balneotherapy.

Cerebral vasoreactivity to carbon dioxide during cardiopulmonary perfusion at normothermia and hypothermia

With the pH-stat acid-base regulation strategy during hypothermic cardiopulmonary bypass (CPB), carbon dioxide (CO2) is generally administered to maintain the partial pressure of arterial CO2 at a higher level than with the alpha-stat method. With preserved CO2 vasoreactivity during CPB, this induction of "respiratory acidosis" can lead to a much higher cerebral blood flow level than is motivated metabolically. To evaluate CO2 vasoreactivity, cerebral blood flow was measured using a xenon 133 washout technique before, during, and after CPB at different CO2 levels in patients who were undergoing coronary artery bypass grafting with perfusion at either hypothermia or normothermia. The overall CO2 reactivity was 1.2 mL/100 g/min/mm Hg. There was no difference between the groups. The CO2 reactivity was not affected by temperature or CPB. The induced hemodilution resulted in higher cerebral blood flow levels during CPB, although this was counteracted by the temperature-dependent decrease in the hypothermia group. After CPB, a transient increase in cerebral blood flow was noted in the hypothermia group, the reason for which remains unclear. The study shows that manipulation of the CO2 level at different temperatures results in similar changes in cerebral blood flow irrespective of the estimated metabolic demand. This finding further elucidates the question of whether alpha-stat or pH-stat is the most physiological way to regulate the acid-base balance during hypothermic CPB.

Acute acoustic trauma. A retrospective study of influencing factors and different therapies in 268 patients

The files of 268 patients with acute acoustic trauma acquired during military service were analysed in a retrospective study. The following factors were examined: age, profession, degree of hearing loss, audiometric contour, and drug treatment. No influence of age or profession on recovery of hearing loss could be detected. The absolute hearing gain, defined as the difference between the hearing loss at onset and, on average, 7 days later, was dependent on the degree of initial hearing loss. The relative hearing gain, defined as absolute hearing gain divided by initial hearing loss, was independent of the degree of initial injury. The audiometric contour after the acoustic trauma had no prognostic relevance. Nine different types of drug treatment were compared in a subgroup of patients (n=199), in all of whom treatment was started within 2 days of the acoustic trauma. There were no significant differences in relative hearing gain between the nine types of treatment. Patients receiving early treatment had significantly better hearing one week after the acoustic trauma, as compared with the group of patients (n=69) not receiving treatment during the first 7 days. However, it was not possible to determine retrospectively whether this difference was due to treatment effects, or whether it was due to the exclusion of spontaneous remissions among those who were neither examined nor treated within the first 7 days.

Addition of misonidazole, etanidazole, or hyperthermia to treatment with fluosol-DA/carbogen/radiation

The antitumor efficacy of adding the nitroimidazole radiosensitizing drugs misonidazole and etanidazole or hyperthermia (43 degrees C for 30 min) to Fluosol-DA/carbogen (95% O2/5% CO2) and irradiation was tested in the FSaIIC tumor system. Both the nitroimidazole drugs and hyperthermia produced additional tumor growth delays and tumor cell cytotoxicity when given with Fluosol-DA/carbogen, either before or after irradiation. For each of the modalities tested, the dose-modifying effect was greater when that therapy preceded rather than followed irradiation (misonidazole 2.7 vs. 1.9, etanidazole 2.4 vs. 1.7, hyperthermia 4.0 vs. 1.7 relative to the effect of radiotherapy alone). Because the nitroimidazole drugs must be present before radiation is administered to exert their radiosensitizing effect, the increase in tumor growth delay observed when these drugs cytotoxic to hypoxic cells were administered following Fluosol-DA/carbogen and irradiation suggests that Fluosol-DA/carbogen could not fully oxygenate the tumors and that the nitroimidazole drugs were effectively toxic to residual hypoxic cells. The treatment Fluosol-DA/carbogen----hyperthermia----irradiation produced a marked increase in tumor growth delay not seen with the sequence Fluosol-DA/carbogen----irradiation----hyperthermia. The results indicate that a treatment combination of radiation sensitizers may be more effective than irradiation plus Fluosol-DA with oxygen breathing alone.

["Dry" carbon dioxide baths in treating patients with myocardial infarction at the sanatorium stage of rehabilitation]

A group of 75 patients with a history of myocardial infarction and repeated myocardial infarction were subjected to treatment involving dry carbon dioxide baths. Its results demonstrated normalization of IHD manifestations, such as coronary and heart failure, functional state of the cardiovascular system, its reserve potentialities and adaptation to physical effort. Under the influence of a course treatment with dry carbon dioxide baths hemodynamic parameters of cardiac output (cardiac and stroke volume) underwent favourable changes, rhythm slowed down, diastole became longer and systolic and diastolic arterial pressure decreased. The data obtained substantiate application of dry carbon dioxide baths in the recovery period to I-III functional classes patients with a history of myocardial infarction.

New high O2 carrying perfluorochemical emulsions and/or carbogen: reactions of a human tumor xenograft to irradiation

The effects of two new perfluorochemical emulsions based on F-66E and PFOB which carry, in combination with carbogen, more oxygen than Fluosol-DA 20% were investigated on a human tumor xenograft (HRT18). Tumor bearing mice were pretreated with 15 ml/kg of F-66E emulsion (50 w/v%) or PFOB (100 w/v%) emulsion in the presence of carbogen for 1 hr prior to and during irradiation. F-66E emulsion was non toxic in vitro. In vivo, the dose modifying factor was 1.8 for mice pretreated with carbogen and F-66E emulsion whereas it was 1.6 for carbogen-breathing mice. Results with PFOB emulsion were similar to those obtained with F-66E emulsion. The effect of F-66E emulsion was studied using a fractionated radiation treatment: 12 Gy were delivered in 6 fractions of 2 Gy with an interval of 8 hrs between fractions. A single dose of F-66E emulsion was injected before the first irradiation. Surviving fractions were 0.35 for air-breathing mice, 0.091 for carbogen-breathing mice and 0.099 for carbogen-breathing mice pretreated with F-66E emulsion. These results showed that carbogen alone or carbogen plus F-66E or PFOB emulsion were very efficient even with low doses of radiation.

Variation in tumor response to fluosol-DA (20%)

The effects of Fluosol-DA 20% (FDA) and carbogen (95% O2/5% CO2) on radiosensitivity of the three experimental tumors, SCC VII tumor, RIF-I tumor, and transplanted mammary tumor of C3H/He mouse, subcutaneously inoculated in the leg were examined. The effect of FDA plus carbogen, and carbogen alone on radiosensitivity of SCC VII and RIF-I tumors was tested using the in vivo-in vitro assay. The growth curves were obtained for both SCC VII tumor and transplanted mammary tumor. The effect of the combination of FDA and carbogen was only observed in the transplanted mammary tumor. In the other two tumors, only the effect of inspiring carbogen was observed. We concluded that the effect of FDA on the radiosensitivity of experimental tumors varies with the kind of tumor systems.

Intermittent use of a perfluorochemical emulsion (Fluosol-DA 20%) and carbogen breathing with fractionated irradiation

Oxygen carrying perfluorochemical emulsions have been shown to enhance the response of animal tumors to large single doses of radiation. Clinically, however, perfluorochemical emulsions are being used with only some fractions in multiple fraction radiation courses. To test the efficacy of a perfluorochemical emulsion under conditions that are closer to those used in current clinical trials, BA1112 rat sarcomas were treated with three fractions per week of 6 Gy per fraction. Once a week, animals were infused i.v. with a perfluorochemical emulsion at 15 ml/kg, and allowed to breathe carbogen (95% O2:5% CO2) for 30 minutes prior to and during irradiation. The 50% tumor control dose was 93.1 (87.9-103.1) Gy in the control arm compared to 74.3 (64.9-83.9) Gy for the animals given the perfluorochemical infusion plus carbogen breathing. The dose modification factor for intermittent perfluorochemical infusion and carbogen breathing was 1.26 (1.15-1.40). In a similar fractionated schedule, the hypoxic cell radiosensitizer, misonidazole, given once per week at 600 mg/kg, gave a dose modification factor of 1.22 (1.14-1.32).

Effect of Fluosol-DA on the response of intracranial 9L tumors to X rays and BCNU

Treatment with a perfluorochemical emulsion combined with breathing a 95% or 100% oxygen atmosphere has been shown to be an effective adjuvant to radiation therapy in several animal tumor systems. Similarly, the addition of treatment with a perfluorochemical emulsion combined with breathing a high oxygen atmosphere has been shown to improve the response of several animal tumor systems to treatment with BCNU. We now report results of the use of the perfluorochemical emulsion, Fluosol-DA, and carbogen breathing with single dose radiation treatment, BCNU and combined drug and radiation treatment in intracranially implanted 9L gliosarcoma. The median enhancement in life span produced by Fluosol-DA and carbogen breathing in addition to radiation was 2 days at 10 Gy and 6 days at 20 Gy compared to radiation treatment alone. In the group receiving 20 Gy with Fluosol-DA and carbogen breathing, 2 of 20 lived 120 days. Treatment with a single intraperitoneal injection of BCNU (10 mg/kg) on day 7 post tumor cell implantation produced an increase in life span of 2 days compared to untreated control animals. The combination of drug treatment with Fluosol-DA and carbogen breathing produced an increase in life span of 26 days, which was significantly different from BCNU treatment with air breathing (p less than 0.001). Finally, when BCNU and Fluosol-DA and carbogen were combined with radiation treatment (20 Gy), an increase in life span of nearly 85 days compared to untreated controls was produced, with 47% (9 or 19) surviving 120 days. These results suggest that this combination might be effective in the treatment of malignant brain tumors.

Preclinical studies of a perfluorochemical emulsion as an adjunct to radiotherapy

Tumor growth and tumor cell survival endpoints were used to examine the effects of a perfluorochemical emulsion, Fluosol-DA, 20%, and carbogen (95% O2/5% CO2) on EMT6 mouse mammary tumors in BALB/c mice. These studies defined the effects of the Fluosol dose on the hematocrit and fluorocrit of the mice and on the radiation response of the tumors. The effect of varying the duration of carbogen breathing before irradiation was examined; times of 5-60 min gave similar enhancements of tumor radiosensitivity. Potentiating effects were not observed when the tumors were irradiated 1-3 days after Fluosol injection, probably reflecting the observed clearance of the perfluorochemicals from the circulating blood. Fluosol injected 30 min-2 days before irradiation did not alter the radiation response of tumors in air-breathing or N2-asphyxiated mice. Together, these studies provided additional support for the hypothesis that the potentiation of tumor radiation response observed after treatment with Fluosol plus carbogen results from changes in O2 delivery to the hypoxic tumor cells by oxygenated perfluorochemical particles. This confirms the conclusion drawn on the basis of the observed changes in the tumor cell survival curve. Studies of tumor cell survival, tumor cell yield, tumor growth, and artificial lung metastasis formation revealed no effects of Fluosol treatment (without irradiation) on tumor progression or metastasis. Studies examining the effects of Fluosol plus carbogen on the growth of tumors irradiated with 5 Gy showed that the changes in tumor radiosensitivity observed using cell survival endpoints also occurred in tumors left in situ after irradiation with a radiation dose similar to those used in some clinical trials.

[Radiosensitizing effects of perfluorochemicals]

Malignant neoplasms are often refractory to radiotherapy because they contain areas of hypoxic cells that tolerate irradiation, reducing the effect of the treatment. If these areas of hypoxic cells can be oxygenated, the effect of radiotherapy is expected to be enhanced. Hyperbaric oxygen therapy was devised in the 1950s, and the radiosensitizing agent Misonidazole was developed in 1970. However, neither produced satisfactory clinical effects in radiotherapy of tumors. In this study, hypoxic cells in a solid tumor were efficiently oxygenated by the use of perfluorochemicals (PFC) developed as artificial blood with carbogen gas (CG), and the anti-tumor effect of irradiation was enhanced. In C3H mice bearing RIF-1 tumor, the mean oxygen pressure increased to 79.8 mmHg in those treated with PFC and CG as compared with 12.9 mmHg in the controls, and the does modification factor in irradiation of these mice was TCD50 1.47. PFC is currently under clinical trials, and we also noted effective oxygenation of tumors. These findings indicate the usefulness of PFC as a radiosensitizing agent.

Effect of carbon dioxide in acute mountain sickness: a rediscovery

The effect of adding CO2 to inhaled air in six subjects with acute mountain sickness was investigated during a medical expedition to 5400 m.3% CO2 in ambient air increased ventilation and resulted in a rise in PaO2 of between 24% and 40%. There was a 9-28% increase in PaCO2 and a reduction of the respiratory alkalosis normally seen at high altitude. Symptoms of acute mountain sickness were rapidly relieved. In three subjects cerebral blood flow increased by 17-39%, so that oxygen delivery to the brain would have been considerably improved. This study confirms earlier suggestions of the beneficial effect of CO2 inhalation at high altitude.

Rebreathing to cope with hyperventilation: experimental tests of the paper bag method

To explore if and how the common rebreathing (paper bag) approach to hyperventilation works, two experiments were carried out. In the first experiment, 12 normal volunteers, aware of the common physiological rebreathing rationale, were twice asked to overbreath intensely and then either to rebreath or to restart normal ventilation. Alveolar CO2 increased more quickly and physical symptoms disappeared earlier in the rebreathing condition. The second experiment had a similar design; however, this time the subjects were led to believe that, after both hyperventilation provocation tests, they were rebreathing in a semiclosed tube system. On one of the occasions, the tube system was, in fact, open. The CO2 restoration again differed in the two conditions. In this second experiment, the moment of symptom disappearance was not significantly earlier in the rebreathing condition. The combined results of the studies suggest that expectation and suggestion play a role in the effects of rebreathing approaches on hyperventilation.

Sudden hearing loss: an update

Etiologic theories of idiopathic SHL include viral infection, autoimmune disease, vascular insult, and labyrinthine membrane rupture. A review of recent literature on sudden hearing loss indicates that scientific support for viral and autoimmune etiologic mechanisms is increasing. Recently studied treatment protocols include carbogen inhalation and steroid therapy. In patients with moderate hearing losses, oral steroids may be beneficial.

Oxygenation effect of fluosol-DA on hypoxic tumor tissue and retention of PFCs in the tumor-bearing rats

An i.v. injection of Fluosol-DA 20% without hydroxy-ethylstarch in combination with carbogen (95% Oz and 5% COz) elevated dose-dependently the tumor POz in AH-109A tumor-bearing rats. The elevation of the tumor PO2 by the treatment of Fluosol-DA injection and carbogen breathing was significantly high at the period when the elevated tumor blood flow declined to the original level and lasted for 3 hours following Fluosol injection. Saline injection with carbogen induced a small increase in the tumor PO2. These results suggest that the oxygenation effect of Fluosol was primarily attributed to the oxygen carrying effect of Fluosol itself. The tumor PO2 increased almost linearly with the arterial PO2. The enhancement in tumor growth delay was observed on the 1 hour post 60CO -ray irradiation with carbogen following Fluosol injection in the Lewis lung tumor-bearing BDF; mice, but not with the 1 day-post irradiation. No significant differences were observed in perfluorochemical retention from the blood circulation and in organ distribution between the tumor bearing rats and normal rats.