Interstitial low-dose-rate brachytherapy as a salvage treatment for recurrent head-and-neck cancers: long-term results.

PURPOSE: Recurrent cancers of the head and neck within previously irradiated volume pose a serious therapeutic challenge. This study evaluates the response and long-term tumor control of recurrent head-and-neck cancers treated with interstitial low-dose-rate brachytherapy. METHODS AND MATERIALS: Between 1979 and 1997, 220 patients with prior radiation therapy with or without surgery for primary tumors of the head and neck were treated for recurrent disease or new primary tumors located within previously irradiated volumes. A majority of these patients had inoperable diseases with no distant metastasis. There were 136 male and 84 female patients, and median age was 56 years. All patients had previously received radiation therapy as the primary treatment or adjuvant treatment following surgery, with a median dose of 57.17 cGy (range, 39-74 cGy). The salvage brachytherapy consisted of a low-dose-rate, afterloading Iridium(192) implant, which delivered a median minimum tumor dose of 53 Gy to a mean tumor volume of 68.75 cm(2). Sixty percent of the patients also received interstitial hyperthermia, and 40% received concurrent chemotherapy as a radiosensitizing and potentiating agent. RESULTS: At a minimum 6-month follow-up, local tumor control was achieved in 77% (217/282) of the implanted tumor sites. The 2, 5, and 10-year disease-free actuarial survival rates for the entire group were 60%, 33%, and 22%, respectively. The overall survival rate for the entire group at 5 years was 21.7%. Moderate to severe late complications occurred in 27% of the patients. CONCLUSION: It has been estimated that approximately 20-30% of head-and-neck cancer patients undergoing definitive radiation therapy have recurrence within the initial treatment volume. Furthermore, similar percentages of patients who survive after successful irradiation develop new primary tumors of the head and neck or experience metastatic neck disease. A majority of such patients cannot be treated with a repeat course of external beam irradiation because of limited normal tissue tolerance, leading to unacceptable morbidity. However, in a select group of these patients, salvage interstitial brachytherapy may play an important role in providing patients with durable palliation and tumor control, as well as a chance for cure.

Simultaneous measurement of intracellular nitric oxide and free calcium levels in chordate eggs demonstrates that nitric oxide has no role at fertilization.

At fertilization in sea urchin, the free radical nitric oxide (NO) has recently been suggested to cause the intracellular Ca(2+) rise responsible for egg activation. The authors suggested that NO could be a universal activator of eggs and the present study was set up to test this hypothesis. Intracellular NO and Ca(2+) levels were monitored simultaneously in eggs of the mouse or the urochordate ascidian Ascidiella aspersa. Eggs were either fertilized or sperm extracts microinjected. Sperm-induced Ca(2+) rises were not associated with any global, or local, change in intracellular NO, although we were able to detect NO produced by the addition of a NO donor. Furthermore, the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester had no effect on sperm-induced Ca(2+) release but did block completely ionomycin-induced NO synthase activation. Therefore, we suggest that the current data provide evidence that NO has no role in the fertilization of these two chordate eggs.

Ca2+ oscillations and the cell cycle at fertilisation of mammalian and ascidian eggs.

At fertilisation of mammalian and ascidian eggs the sperm induces a series of Ca2+ oscillations. These Ca2+ oscillations are triggered by a sperm-borne Ca2+-releasing factor whose identity is still unresolved. In both mammals and ascidians Ca2+ oscillations in eggs are associated with the period leading up to exit from meiosis and entry into the first embryonic cell cycle. Thus, in mammals Ca2+ oscillations continue for several hours but are complete by within 30 min in the ascidian. In mammals and ascidians Ca2+ oscillations stop at around the time when pronuclei form in the 1-cell embryo. There is evidence to show that cell cycle factors are important in regulating the fertilisation Ca2+ signal. If the formation of pronuclei is blocked either in mammals (by spindle disruption) or in ascidians (by clamping maturation promoting factor levels high) then Ca2+ oscillations continue indefinitely. Here, we explore the nature of the sperm Ca2+-releasing factor and examine the relationship between cell cycle resumption and the control of Ca2+ oscillations at fertilisation.

Sperm-induced Ca(2+) oscillations in mouse oocytes and eggs can be mimicked by photolysis of caged inositol 1,4,5-trisphosphate: evidence to support a continuous low level production of inositol 1, 4,5-trisphosphate during mammalian fertilization.

During mouse fertilization the spermatozoon induces a series of low-frequency long-lasting Ca(2+) oscillations. It is generally accepted that these oscillations are due to Ca(2+) release through the inositol 1,4,5-trisphosphate (InsP(3)) receptor. However, InsP(3) microinjection does not mimic sperm-induced Ca(2+) oscillations, leading to the suggestion that the spermatozoon causes Ca(2+) release by sensitizing the InsP(3) receptor to basal levels of InsP(3). This contradicts recent evidence that the spermatozoon triggers Ca(2+) oscillations by introducing a phospholipase C or else an activator of phospholipase C. Here we show for the first time that sperm-induced Ca(2+) oscillations may be mimicked by the photolysis of caged InsP(3) in both mouse metaphase II eggs and germinal vesicle stage oocytes. Eggs, and also oocytes that had displayed spontaneous Ca(2+) oscillations, gave long-lasting Ca(2+) oscillations when fertilized or when caged InsP(3) was photolyzed. In contrast, oocytes that had shown no spontaneous Ca(2+) oscillations did not generate many oscillations when fertilized or following photolysis of caged InsP(3). Fertilization in eggs was most closely mimicked when InsP(3) was uncaged at relatively low amounts for extended periods. Here we observed an initial Ca(2+) transient with superimposed spikes, followed by a series of single transients with a low frequency; all characteristics of the Ca(2+) changes at fertilization. We therefore show that InsP(3) can mimic the distinctive pattern of Ca(2+) release in mammalian eggs at fertilization. It is proposed that a sperm Ca(2+)-releasing factor operates by generating a continuous small amount of InsP(3) over an extended period of time, consistent with the evidence for the involvement of a phospholipase C.

Dos, a heme-binding PAS protein from Escherichia coli, is a direct oxygen sensor.

A direct sensor of O(2), the Dos protein, has been found in Escherichia coli. Previously, the only biological sensors known to respond to O(2) by direct and reversible binding were the FixL proteins of Rhizobia. A heme-binding region in Dos is 60% homologous to the O(2)-sensing PAS domain of the FixL protein, but the remainder of Dos does not resemble FixL. Specifically, the C-terminal domain of Dos, presumed to be a regulatory partner that couples to its heme-binding domain, is not a histidine kinase but more closely resembles a phosphodiesterase. The absorption spectra of Dos indicate that both axial positions of the heme iron are coordinated to side chains of the protein. Nevertheless, O(2) and CO bind to Dos with K(d) values of 13 and 10 microM, respectively, indicating a strong discrimination against CO binding. Association rate constants for binding of O(2) (3 mM(-)(1) s(-)(1)), CO (1 mM(-)(1) s(-)(1)) and even NO (2 mM(-)(1) s(-)(1)) are extraordinarily low and very similar. Displacement of an endogenous ligand, probably Met 95, from the heme iron in Dos triggers a conformational change that alters the activity of the enzymatic domain. This sensing mechanism differs from that of FixL but resembles that of the CO sensor CooA of Rhodospirillum rubrum. Overall the results provide evidence for a heme-binding subgroup of PAS-domain proteins whose working range, signaling mechanisms, and regulatory partners can vary considerably.

Direct evidence that the proton motive force inhibits membrane translocation of positively charged residues within membrane proteins.

The M13 phage procoat protein requires both its signal sequence and its membrane anchor sequence in the mature part of the protein for membrane insertion. Translocation of its short acidic periplasmic loop is stimulated by the proton motive force (pmf) and does not require the Sec components. We now find that the pmf becomes increasingly important for the translocation of negatively charged residues within procoat when the hydrophobicity of the signal or membrane anchor is incrementally reduced. In contrast, we find that the pmf inhibits translocation of the periplasmic loop when it contains one or two positively charged residues. This inhibitory effect of the pmf is stronger when the hydrophobicity of the inserting procoat protein is compromised. No pmf effect is observed for translocation of an uncharged periplasmic loop even when the hydrophobicity is reduced. We also show that the Delta Psi component of the pmf is necessary and sufficient for insertion of representative constructs and that the translocation effects of charged residues are primarily due to the DeltaPsi component of the pmf and not the pH component.

Pleomorphic adenoma of the epiglottis: report of a case.

We describe the clinical and pathologic aspects of an unusual case of pleomorphic adenoma of the epiglottis. A 69-year-old man had impaired speech and a "lumpy sensation" in the throat. Following clinical evaluation and a diagnostic biopsy, the tumor was totally excised with excellent results. Pleomorphic adenoma of the larynx is most uncommon. To our knowledge, no report describing the clinical and pathologic features of this entity in the epiglottis or larynx has been previously reported. This is the only example of an epiglottic pleomorphic adenoma among 391 cases seen at Presbyterian-University Hospital and the Eye and Ear Hospital of Pittsburgh during a 21-year period.