Remodeling the cell surface distribution of membrane proteins during the development of epithelial cell polarity.

The development of polarized epithelial cells from unpolarized precursor cells follows induction of cell-cell contacts and requires resorting of proteins into different membrane domains. We show that in MDCK cells the distributions of two membrane proteins, Dg-1 and E-cadherin, become restricted to the basal-lateral membrane domain within 8 h of cell-cell contact. During this time, however, 60-80% of newly synthesized Dg-1 and E-cadherin is delivered directly to the forming apical membrane and then rapidly removed, while the remainder is delivered to the basal-lateral membrane and has a longer residence time. Direct delivery of greater than 95% of these proteins from the Golgi complex to the basal-lateral membrane occurs greater than 48 h later. In contrast, we show that two apical proteins are efficiently delivered and restricted to the apical cell surface within 2 h after cell-cell contact. These results provide insight into mechanisms involved in the development of epithelial cell surface polarity, and the establishment of protein sorting pathways in polarized cells.

Mechanism for regulating cell surface distribution of Na+,K(+)-ATPase in polarized epithelial cells.

Restriction of sodium, potassium adenosine triphosphatase (Na+,K(+)-ATPase) to either the apical or basal-lateral membrane domain of polarized epithelial cells is fundamental to vectorial ion and solute transport in many tissues and organs. A restricted membrane distribution of Na+,K(+)-ATPase in Madin-Darby canine kidney (MDCK) epithelial cells was found experimentally to be generated by preferential retention of active enzyme in the basal-lateral membrane domain and selective inactivation and loss from the apical membrane domain, rather than by vectorial targeting of newly synthesized protein from the Golgi complex to the basal-lateral membrane domain. These results show how different distributions of the same subunits of Na+,K(+)-ATPase may be generated in normal polarized epithelial and in disease states.

Sodium channel expression and assembly during development of retinal ganglion cells.

Acquisition of functional Na+ channels is a critical event in the development of a neuron because it allows the generation of conducted action potentials. alpha subunit mRNA is first detected in developing rat retina at 1% of its maximum level on embryonic day 15, 4 days after the first ganglion cells are formed. alpha subunit protein is detected in the axons of the ganglion cells at this time, but beta 1 subunits, beta 2 subunits, and high affinity saxitoxin binding sites are not detected until after birth. There is an approximately coordinate increase in alpha subunit mRNA, alpha, beta 1, and beta 2 subunit protein, assembled complexes of alpha, beta 1, and beta 2 subunits, and high affinity saxitoxin binding sites between postnatal days 7 and 21. Expression of alpha subunit genes is an early event in ganglion cell differentiation, and both gene transcription and posttranslational assembly are separate, rate-limiting steps in development of Na+ channels.

Antiemetic efficacy of high-dose dexamethasone versus placebo in patients receiving cisplatin-based chemotherapy: a randomized double-blind controlled clinical trial.

The antiemetic effect of short courses of high-dose dexamethasone was compared with that of placebo in 64 patients receiving cisplatin-based cancer chemotherapy, in a double-blind randomized clinical trial. All patients were receiving cisplatin for the first time. Dexamethasone was given intravenously (IV) at a dose of 20 mg, two hours before and 3, 6, 9, and 12 hours after chemotherapy. Patients were crossed over to dexamethasone on the second cycle of chemotherapy if they experienced unacceptable gastrointestinal (GI) toxicity after initial treatment with placebo. Nine of 32 patients receiving dexamethasone and seven of 32 patients receiving placebo did not vomit. The median duration of nausea was significantly shorter (one-half hour) for the dexamethasone-treated group compared with that of placebo (31/2 hours). The number of patients who experienced unacceptable GI toxicity was significantly greater (53%) for the placebo patients than for those treated with dexamethasone (25%). Patients crossing over to dexamethasone after initially receiving placebo had a median duration of nausea of 11/2 hours and 24% did not vomit, results comparable to the first treatment group. We conclude that high-dose dexamethasone is only minimally effective as an antiemetic agent in patients receiving cisplatin-based chemotherapy.

Hypercalcemia in prostatic carcinoma. Report of eight cases.

Hypercalcemia is a rare complication of disseminated carcinoma of the prostate. To our knowledge, only three such patients have had their cases previously reported in the English language literature. Eight patients with prostatic cancer and hypercalcemia were seen at Montefiore Hospital and Medical Center, Bronx, NY, within the last six years. In six of the patients, the prostatic carcinoma exhibited unusual histologic patterns.

A comparative trial of moxalactam plus ticarcillin and clavulanic acid or piperacillin as empiric antibiotic therapy for febrile cancer patients.

Resistance of bacteria to beta-lactam antibiotics remains a difficult clinical problem that can be compounded in infected patients with serious underlying illness, especially those who are immunocompromised. In a prospective randomized safety and efficacy trial, febrile cancer patients received either ticarcillin disodium combined with the beta-lactamase inhibitor clavulante potassium (Timentin, Beecham Laboratories, Bristol, TN) plus moxalactam (T+M), or piperacillin plus moxalactam (P+M) as initial empiric antimicrobial therapy. Sixty-six febrile episodes in 53 patients were studied. In the T+M group, 14 (78%) of 18 clinically evaluable infections in patients with profound granulocytopenia improved as did all 14 (100%) such infections in the P+M group. In the T+M group 17 of 21 (81%) similarly evaluable infections improved irrespective of granulocyte count, as did 14 (88%) of 16 of such infections in the P+M group. These results are not statistically significantly different. Serious side effects were infrequent and comparable with both regimens. There was one antibiotic related hemorrhage in the P+M group and a serious episode of nephrotoxicity in a patient who died without recovering renal function in the T+M group. These results suggest that the overall safety and efficacy of Timentin plus moxalactam, and piperacillin plus moxalactam are comparable and similar to previous empiric antibiotic trials.

Antigenic differences among the voltage-sensitive sodium channels in the peripheral and central nervous systems and skeletal muscle.

Antisera prepared against the voltage-sensitive sodium channel purified from rat brain are able to distinguish antigenic differences between the sodium channels in peripheral nerve tissue, the central nervous system, and in skeletal muscle. These results indicate that, in spite of many well-documented similarities among the sodium channels of all excitable tissues, there are biochemical differences that may prove important in future studies of the regulation and molecular mechanisms of electrical excitability.

End of life care and decision making: how far we have come, how far we have to go.

While enormous progress has been made in improving the quality of care and the decision-making process for patients at the end of life, as a society we still have far to go to ensure that dying patients and their families have a comfortable and dignified death. In particular, reexamination and reconfiguration of our current decision framework is essential as our elderly population with chronic disease and slowly fatal conditions expands. With less certain disease paths and more complex and ambiguous choices, the growth of this geriatric population challenges us to develop a broader conceptualization of end of life care planning, so that end of life considerations are integrated into a larger anticipatory framework addressing options and needs as patients gradually decline. Within this framework hospice becomes a natural, integrated option along a continuum of care planning, rather than an abrupt alternative at a late stage of illness. End of life care planning must positively anticipate a robust array of needs and concerns well beyond the dramatic decisions to withhold or withdraw life-prolonging technologies usually found in advance directives. To embrace this broader framework it is critical that primary care physicians as well as disease specialists receive training in fundamental aspects of both geriatric and palliative care. Professionals from both of these disciplines must share expertise with each other, and should collaborate in advocacy efforts to effectuate changes in the clinical, policy and legislative arenas.

Localization of sodium channels in axon hillocks and initial segments of retinal ganglion cells.

Affinity-purified antibodies against the sodium channel from rat brain were employed to localize sodium channels in the retina by immunocytochemical procedures. In rat retina, intense staining was observed in the ganglion cell axon layer and light staining was detected in fibers of the inner plexiform layer. In frog retina, only the ganglion cell axon layer was stained. Examination at higher magnification revealed that axon hillocks and initial segments of ganglion cells had a high density of immunoreactive sodium channels, whereas the cell bodies were devoid of stain. The sharply defined region of high sodium channel density at the axon hillock is likely to be responsible for the low threshold for action potential initiation in this region of vertebrate central neurons.

Beta 2 subunits of sodium channels from vertebrate brain. Studies with subunit-specific antibodies.

The sodium channel purified from rat brain is composed of three subunits: alpha (Mr 260,000), beta 1 (Mr 36,000), and beta 2 (Mr 33,000). alpha and beta 2 subunits are linked through disulfide bonds. Procedures are described for preparative isolation of the beta 1 and beta 2 subunits under native conditions. Pure beta 2 subunits obtained by this procedure were used to prepare a specific anti-beta 2 subunit antiserum. Antibodies purified from this serum by antigen affinity chromatography recognize only disulfide-linked alpha beta 2 complexes and beta 2 subunits in immunoblots, and immunoprecipitate 32P-labeled alpha subunits of purified sodium channels having intact disulfide bonds, but not those of sodium channels from which beta 2 subunits have been detached by reduction of disulfide bonds. These antibodies also immunoprecipitate 89% of the high affinity saxitoxin-binding sites from rat brain membranes, indicating that nearly all sodium channels in rat brain have disulfide-linked alpha beta 2 subunits. Approximately 22% of beta 2 subunits in adult rat brain are not disulfide-linked to alpha subunits. Anti-beta 2 subunit antibodies are specific for sodium channels in the central nervous system and will not cross-react with sodium channels in skeletal muscle or sciatic nerve. The brains of a broad range of vertebrate species, including electric eel, are shown to express sodium channels with disulfide-linked alpha beta 2 subunits.

Ovarian cancer. Effective treatment after alkylating-agent failure.

Combination chemotherapy consisting of hexamethylmelamine and cisplatin, alone or with doxorubicin hydrochloride, was given to 27 patients with advanced ovarian cancer who had disease progression with therapy including alkylating agents. Eighteen (67%) had greater than 50% regression of measurable disease or disease that could be evaluated but not measured, for a projected median duration of seven months. The projected median survival for all patients is nine months from the time of entry into the study and 33 months from the time of diagnosis of ovarian cancer. The treatment could be readily administered on an outpatient basis with a regimen of hydration and diuresis that nearly completely prevented platinum-induced renal tubular damage. Myelosuppression was severe in 11 patients (40%), but there was no treatment-related deaths. Agents of such high activity should be considered as components of initial therapy for stage III and IV cancers.

Biochemical properties of sodium channels in a wide range of excitable tissues studied with site-directed antibodies.

Antibodies against a peptide (SP19) corresponding to a highly conserved, predicted intracellular region of the sodium channel alpha subunit bind rat brain sodium channels with a similar affinity as the peptide antigen, indicating that the corresponding segment of the alpha subunit is fully accessible in the intact channel structure. These antibodies recognize sodium channel alpha subunits from rat or eel brain, rat skeletal muscle, rat heart, eel electroplax, and locust nervous system. alpha subunits from all these tissues except rat skeletal muscle are substrates for phosphorylation by cAMP-dependent protein kinase. Disulfide linkage of alpha and beta 2 subunits was observed for both the RI and RII subtypes of rat brain sodium channels and for sodium channels from eel brain but not for sodium channels from rat heart, eel electroplax, or locust nerve cord. Treatment with neuraminidase reduced the apparent molecular weight of sodium channel alpha subunits from rat and eel brain and eel electroplax by 22,000-58,000, those from heart by 8000, and those from locust nerve cord by less than 4000. Our results provide the first identification of sodium channel alpha subunits from rat heart and locust brain and nerve cord and show that sodium channel alpha subunits are expressed with different subunit associations and posttranslational modifications in different excitable tissues.

Effect of tamoxifen treatment on cortisol metabolism and the course of the disease in advanced breast cancer.

Twenty-nine postmenopausal women with advanced breast cancer were treated with Tamoxifen, a nonsteroidal antiestrogen. The effect of the drug on the plasma concentration, production rate, and metabolism of cortisol was measured, and the relationship of the changes in these parameters to the course of the disease was investigated. After six weeks of Tamoxifen treatment the plasma cortisol concentration and the cortisol-binding globulin concentration increased by 26 and 64%, respectively, but the production rate of cortisol and the urinary excretion of its tetrahydro metabolites THF, ATHF, and THE decreased by 35 and 13%, respectively; all of these changes were statistically significant. When the group consisting of complete or partial responders was compared with one consisting of patients whose disease remained stable or worsened, no significant difference was detected between these two groups in the change in any of the above parameters. It was concluded that any improvement due to Tamoxifen was not related to changes in cortisol metabolism.