Prevalence and distribution of ret/ptc 1, 2, and 3 in papillary thyroid carcinoma in New Caledonia and Australia.

The world's highest incidence of thyroid cancer has been reported among females in New Caledonia, a French overseas territory in the Pacific located between Australia and Fiji. To date, no molecular genetic studies in this population are available. Over the past few years, the oncogenic rearrangement of the ret protooncogene (ret/ptc) has been studied in papillary carcinomas in different populations. In this study, we investigated the prevalence and distribution of ret/ptc1, 2, and 3 in papillary thyroid carcinoma from the New Caledonian population and compared the pattern with that of an Australian population. Fresh-frozen and paraffin-embedded papillary carcinomas from 27 New Caledonian and 20 Australian patients were examined for ret rearrangements by means of RT-PCR with primers flanking the chimeric region, followed by hybridization with radioactive probes. ret/ptc was present in 70% of the New Caledonian and in 85% of the Australian samples. Multiple rearrangements were detected and confirmed by sequencing in 19 cases, 4 of which had 3 types of rearrangements in the same tumor. This study demonstrates a high prevalence of ret/ptc in New Caledonian and Australian papillary carcinoma. The findings of multiple ret/ptc in the same tumor suggest that some thyroid neoplasms may indeed be polyclonal.

NASA's Advanced Life Support Systems Human-Rated Test Facility.

Future NASA missions to explore the solar system will be long-duration missions, requiring human life support systems which must operate with very high reliability over long periods of time. Such systems must be highly regenerative, requiring minimum resupply, to enable the crews to be largely self-sufficient. These regenerative life support systems will use a combination of higher plants, microorganisms, and physicochemical processes to recycle air and water, produce food, and process wastes. A key step in the development of these systems is establishment of a human-rated test facility specifically tailored to evaluation of closed, regenerative life supports systems--one in which long-duration, large-scale testing involving human test crews can be performed. Construction of such a facility, the Advanced Life Support Program's (ALS) Human-Rated Test Facility (HRTF), has begun at NASA's Johnson Space Center, and definition of systems and development of initial outfitting concepts for the facility are underway. This paper will provide an overview of the HRTF project plan, an explanation of baseline configurations, and descriptive illustrations of facility outfitting concepts.

Parotid and neck metastases from cutaneous squamous cell carcinoma of the head and neck.

BACKGROUND: Approximately 5% of cutaneous squamous cell carcinomas (SCC) metastasize to regional nodes. Nodal involvement may be more common for cutaneous squamous cell carcinomas of the head and neck, but few large series have reported clinical outcome after treatment of parotid gland and neck metastases from these cancers. PATIENTS AND METHODS: A combined retrospective/prospective study of patients treated between 1983 and 1994 was performed. There were 69 men and 6 women, with a median age of 67 years. Twenty-nine patients had neck metastases, and 33 had parotid gland metastases, while 13 patients had involvement at both sites. Of the 75 patients, 68 were treated surgically and 50 received postoperative radiotherapy. RESULTS: The facial nerve was sacrificed totally in 6 patients and partially in 9. Histologic extranodal spread was present in 48 (71%) of all surgically treated patients. Among 61 patients followed up to recurrence, or for greater than 12 months, 26 (43%) developed recurrence--12 in the parotid gland, 7 in the neck, and 7 in both sites. Multiple recurrences were common and occurred at a median of 8 months after surgery. Positive surgical margins were associated with poorer local disease control (P < 0.05). Cumulative survival at 5 years was 61%, but only 15 of 70 evaluable patients (21%) were eligible for follow-up at this time. Neck involvement with or without parotid gland disease was associated with an increased risk of distant metastases, but this was not statistically significant. Postoperative radiotherapy was not associated with improved disease control. CONCLUSION: Cutaneous, metastatic SCC involving the parotid gland and neck is an aggressive disease with a tendency to an infiltrative growth pattern and multiple recurrences. More aggressive surgery may be justified to reduce the incidence of regional failure after parotidectomy and neck dissection.

Limitations of radiotherapy in the definitive treatment of squamous carcinoma of the tonsillar fossa.

Between 1970 and 1990, 104 patients with squamous cell carcinoma (SCC) of the tonsil were treated. The median age was 58 years and 80% of patients were males. Distribution among clinical stages was: stage I, 19 patients; stage II, 12 patients; stage III, 23 patients; and stage IV, 48 patients. More than 70% of patients had initial radiotherapy as definitive treatment irrespective of stage, reflecting the treatment philosophy over much of this period. The overall survival rate was 26% at 5 years, with survival being significantly affected by T stage, clinical stage and age. Clinical node status did not significantly affect survival rates. Good local control of T1N0 cancers was achieved with radiotherapy alone, but patients with more advanced cancers did poorly. We have now moved away from a non-selective policy and use initial surgery combined with postoperative radiotherapy in most patients, reserving radiotherapy alone for mainly early tonsil cancers.

Is the 9 kDa thylakoid membrane phosphoprotein functionally and structurally analogous to the 'H' subunit of bacterial reaction centres?

Although the amino acid sequence of the 9 kDa (phospho)protein of chloroplasts has been determined, the function of this thylakoid membrane protein in photosynthetic electron transport and the reason for its physiological control remains unclear. In this paper, I briefly review the evidence which indicates that the phosphorylation of the 9 kDa protein results in a partial inhibition of photosynthetic oxygen evolution by increasing the stability of the semiquinone bound to QA the primary, plastoquinone-binding site of photosystem II (PS II). I propose that in its dephosphorylated state, the 9 kDa thylakoid membrane protein may serve PS II to ensure efficient photochemical charge separation by aiding the transfer of reducing equivalents out of the reaction centre to the attendant plastoquinone pool. This function is analogous to that proposed for the H-subunit of the reaction centre of photosynthetic eubacteria. Whether these two proteins have evolved from a common ancestral reaction centre protein is discussed in the light of a comparison of their amino acid sequences and predicted secondary structures.

Photoelectric currents across planar bilayer membranes containing bacterial reaction centers: the response under conditions of multiple reaction-center turnovers.

The characteristics of the photocurrent response activated by continuous illumination of planar bilayer membranes containing bacterial reaction centers have been resolved by voltage clamp methods. The photocurrent response to a long light pulse consists of an initial spike arising from the fast, quasi-synchronous electron transfer from the reaction center bacteriochlorophyll dimer, BChl2, to the primary quinone QA. This is followed by a slow relaxation of the current to that promoted by secondary, asynchronous multiple electron transfers from the reduced cytochrome c through the reaction centers to the ubiquinone-10 pool. Currents derived from cytochrome c oxidation that occurs when cytochrome c is associated with the reaction center or when limited by diffusional interaction from solution are recognized. Changes of the ionic strength and pH in the aqueous phase, and the clamped membrane potential (+/- 150 mV), affect the electron-transfer rate between cytochrome c and BChl2. In contrast, the primary light-induced charge separation between BChl2 and QA, or electron transfer between QA on the ubiquinone pool are unaffected. During illumination of reaction center membranes supplemented with cytochrome c and a ubiquinone pool, there is a small but significant steady-state current which is considered to be caused by the re-oxidation of photoreduced quinone by molecular oxygen. In the dark, after illumination of reaction centers supplemented with cytochrome c and a ubiquinone pool, there is a small amount of reverse current resulting from the movement of charges back across the membrane. This reverse current is observed maximally after 400 ms illumination while prolonged illumination diminishes the effect. The source of this current is uncertain, but it is considered to be due to the flux of anionic semiquinone within the membrane profile; this may also be the species that interacts with oxygen giving rise to the steady-state current. It is postulated that when the reaction centers are contained in an alkane-containing phospholipid membrane, in contrast to the in vivo situation, the semiquinone anion formed in the QB site is not tightly bound to the site and can, by exchange-diffusion with the membrane-quinone pool, move away from the site and accumulate in the membrane. However, in the absence, more quantitative work superoxide anion, resulting from O2 interaction with semiquinone of QA, QB or pool cannot be excluded.

Changes in the flash-induced oxygen yield pattern by thylakoid membrane phosphorylation.

Phosphorylation of thylakoid membrane proteins results in a partial inhibition (approximately 15-20%) of the light-saturated rate of oxygen evolution. The site of inhibition is thought to be located on the acceptor side of photosystem 2 (PS2) between the primary, QA, and secondary, QB, plastoquinone acceptors (Hodges et al. 1985, 1987). In this paper we report that thylakoid membrane phosphorylation increases the damping of the quaternary oscillation in the flash oxygen yield and increases the extent of the fast component in the deactivation of the S2 oxidation state. These results support the proposal that thylakoid membrane protein phosphorylation decreases the equilibrium constant for the exchange of an electron between QA and QB. An analysis of the oxygen release patterns using the recurrence matrix model of Lavorel (1976) indicates that thylakoid membrane phosphorylation increases the probability that PS2 miss a S-state transition by 20%. This is equivalent, however, to an insignificant inhibition (approximately 2.4%) of the light-saturated oxygen evolution rate. If a double miss in the S-state transitions is included when the PS2 centres are in S2 the fit between the experimental and theoretical oxygen yield sequences is better, and sufficient to account for the 15-20% inhibition in the steady-state oxygen yield. A double miss in the S-state transition is a consequence of an increased population of PS2 centres retaining QA (-): not only will these PS2 centres fail to catalyse photochemical charge transfer until QA (-) is reoxidized, but the re-oxidation reaction will also result in the deactivation of S2 to S1.

Treatment of advanced and inaccessible sarcomas with continuous intra-arterial chemotherapy prior to definitive surgery or radiotherapy--a possible alternative to amputation or disabling radical surgery.

Four patients with advanced and inaccessible soft tissue sarcomas were treated with a regimen of intra-arterial chemotherapy followed by radiotherapy and/or surgical excision. Two of the patients had advanced sarcomas in the buttock and thigh regions which would otherwise have required hindquarter amputation in one case or disarticulation of the hip in the other case. These sarcomas responded significantly to intra-arterial chemotherapy to the extent that subsequent local surgery was effective in eradicating the residual tumours. No viable tumour cells were found in the resected specimens. In both patients amputation was avoided and local tumour eradication was achieved. In the other two patients, advanced and non-resectable sarcomas in the head were first treated with a similar regimen of intra-arterial chemotherapy. In both cases the tumours regressed in size prior to administration of local radiotherapy. After completion of chemotherapy and radiotherapy no viable tumour cells were detected in either lesion. In one case (originally a very extensive sarcoma of the jaw in a 5 year old child) a residual lump was resected but no viable tumour was detected in the resected specimen. These four patients represent our total experience with this plan of management. All responded well and there has been no evidence of local disease recurrence in any of the four patients. One patient (Case 2) did develop pulmonary and bone metastases from which she died 2 years later but the other three patients remain well with no evidence of residual disease, 11 years, 4 years and 20 months after presentation.

The light-intensity-dependence of the efficacy of 2-(3-chloro-4-trifluoromethyl)-anilino-3,5-dinitrothiophene (Ant2p) to inhibit the photosystem 2 reactions of chloroplasts.

The mechanism by which Ant2p [2-(3-chloro-4-trifluoromethyl)anilino-3, 5-dinitrothiophene] inhibits the oxygen evolution capacity of chloroplasts is thought to be due to a rapid reduction of the S2 and S3 oxidation states of the oxygen-evolving complex mediated by the oxidation of endogenous donors such as cytochrome b559. The results presented in this paper show that the degree of inhibition by Ant2p of the photosystem 2-supported electron transfer reactions, registered by the light-dependent rate of dichlorophenolindophenol reduction, varies according to the actinic light intensity. Moreover, a similar intensity-dependence can be detected in the extent of the Ant2p-induced cytochrome b559HP photo-oxidation. We show, however, that the dependence of the cytochrome oxidation is not due to the oxidation per se, but reflects changes in the high light-driven re-reduction reaction. The close correlation between the two Ant2p reactions is interpreted as indicating that the effect of Ant2p might be due to an inhibition of the S-state turnovers and not necessarily due to a deactivation process.

Photoelectric currents across planar bilayer membranes containing bacterial reaction centers. Response under conditions of single electron turnover.

Light-induced electric current and potential responses have been measured across planar phospholipid membranes containing reaction centers from the photosynthetic bacterium Rhodopseudomonas sphaeroides. Under conditions in which the reaction centers are restricted to a single electron turnover, the responses can be correlated with the light-induced electron transfer reactions associated with the reaction center. The results indicate that electron transfer from the bacteriochlorophyll dimer to the primary ubiquinone molecule, and from ferrocytochrome c to the oxidized dimer occur in series across the planar membrane. Electron transfer from the primary to secondary ubiquinone molecule is not electrogenic.

Construction of a flash-activated cyclic electron transport system by using bacterial reaction centers and the ubiquinone-cytochrome b-c1/c segment of mitochondria.

Single-turnover electron transfer within the mitochondrial complex III has been studied by combining, in solution, the isolated complex from bovine heart with detergent-solubilized reaction centers of Rhodopseudomonas sphaeroides. Initiation of electron transfer by short flash activation resulted in the prompt oxidation of cytochrome c and reduction of cytochrome b. The subsequent reduction of ferricytochrome c was observed to be concomitant with the oxidation of the ferrocytochrome b, both reactions being inhibited by the addition of actimycin A. The rate of electron transfer through complex III is dependent upon the ambient redox potential poise in a way that is consistent with the presence of a redox component, presumably analogous to the photosynthetic ubiquinone Qz, which is an obligatory intermediate in electron transfer between cytochromes b and c. These results demonstrate cyclic electron transfer in a constructed assembly of mitochondrial complex III, cytochrome c, and photochemical reaction centers.

Generation of membrane potential during photosynthetic electron flow in chromatophores from Rhodopseudomonas capsulata.

1. When cytochrome c2 is available for oxidation by the photosynthetic reaction centre, the decay of the carotenoid absorption band shift generated by a short flash excitation of Rhodopseudomonas capsulata chromatophores is very slow (half-time approximately 10 s). Otherwise the decay is fast (half-time approximately 1 s in the absence and 0.05 s in the presence of 1,10-ortho-phenanthroline) and coincides with the photosynthetic back reaction. 2. In each of these situations the carotenoid shift decay, but not electron transport, may be accelerated by ioniophores. The ionophore concentration dependence suggests that in each case the carotenoid response is due to a delocalised membrane potential which may be dissipated either by the electronic back reaction or by electrophoretic ion flux. 3. At high redox potentials, where cytochrome c2 is unavailable for photooxidation, electron transport is believed to proceed only across part of the membrane dielectric. Under such conditions it is shown that the driving force for carbonyl cyanide trifluoromethoxyphenyl hydrazone-mediated H+ efflux is nevertheless decreased by valinomycin/K+; demonstrating that the [BChl]2 leads to Q electron transfer generates a delocalised membrane potential.

Transport of local anaesthetics across chromatophore membranes.

1. Both simple amines and tertiary amino local anaesthetics give rise to an accelerated decay of the absorption change of added pH indicator dyes and a decelerated decay of the endogenous carotenoid absorption band shift, following short flash excitation of Rhodopseudomonas sphaeroides chromatophores. 2. With increasing medium pH, lower concentrations of amine or local anaesthetics are effective. 3. The order of potency of the local anaesthetics concurs with their reported membrane/buffer partition coefficients and concentrations required for action potential blockade in nerve fibres. 4. The data are taken as evidence for rapid transport of the free base across the chromatophore membrane and relatively slow penetration of the protonated local anaesthetic. Protolytic reactions complete the effective dissipation of the trans-membrane pH gradient. 5. Benzocaine, with its unusually low pKa and the quaternary derivative, chloropromazine methiodide do not display this type of behaviour. 6. In the presence of membrane potential-collapsing agents, such as valinomycin/K+ or thiocyanate ions, local anaesthetics decelerate the decay of the cresol red change but have no effect on the carotenoid shift decay. It appears that transport of the unprotonated local anaesthetic although electrically neutral, requires the presence of a membrane potential. 7. In contrast, the non-anaesthetic amines act independently of the membrane potential. 8. Ca2+ interferes with the mechanism of local anaesthetic deceleration of the cresol red change decay in the presence of valinomycin/K+ or thiocyanate but not with other anaesthetic or amine reactions.