Sodium nitroprusside/nitric oxide causes apoptosis in spiral ganglion cells

OBJECTIVE

In the cochlea, excitatory amino acid receptor overstimulation induces toxicity in spiral ganglion neurons by an unknown mechanism. In the central nervous system, excitatory amino acid-induced toxicity is mediated by nitric oxide, which induces apoptosis in neurons. This study tested the hypothesis that cochlear nitric oxide-mediated toxicity is the result of induction of apoptosis in spiral ganglion neurons.

METHODS

The cochleas of 15 gerbils randomly assigned to different groups were perfused for 30 minutes with a test solution of 1 mmol/L sodium nitroprusside, a nitric oxide donor, or a control solution of artificial perilymph. Animals were killed at varying times, including 2, 3, 4, 8, and 18 hours after perfusion. DNA fragmentation or in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling analysis was done on cochleas for detection of apoptosis.

RESULTS

Analysis by both techniques demonstrated marked apoptotic cell changes in spiral ganglion neurons of sodium nitroprusside-treated cochleas evident 4 to 8 hours after perfusion, as compared with minimal to no evidence of apoptosis in spiral ganglion neurons of control specimens.

CONCLUSIONS

Exposure to high levels of nitric oxide induces apoptosis in spiral ganglion neurons. Because apoptosis is a delayed, potentially reversible cell death pathway, this may present an opportunity for intervention to prevent or attenuate hearing damage induced by excitotoxic stimuli.

Synthesis and in vitro activity of long-chain 5'-O-[(alkoxycarbonyl)phosphinyl]-3'-azido-3'-deoxythymidines against wild-type and AZT- and foscarnet-resistant strains of HIV-1

Lipophilic esters of 3'-azido-3'-deoxy-5'-O-(carboxyphosphinyl)thymidine (PFA-AZT) were synthesized and tested for antiretroviral activity in CD4+ HT4-6C cells infected with either wild-type HIV-1LAI, a PFA-resistant strain encoding a single-point mutation in reverse transcriptase (E89K), or an AZT-resistant clinical isolate (A018-post). Arbuzov condensation of 1-octadecyl, 1-eicosanyl, and 1-docosanyl chloroformate with trimethyl phosphite yielded the corresponding dimethyl long-chain alkyl triesters of PFA. Selective removal of one methyl group from the triesters with sodium iodide yielded monosodium salts, whereas treatment with bromotrimethylsilane cleaved both methyl groups while leaving the long-chain alkyl group intact. Neutralization of the resulting [(alkyloxy)carbonyl]phosphonic acids with 2 equiv of sodium methoxide afforded disodium salts of the phosphonic acid moiety. Similar chemistry was used to obtain the mono- and disodium salts of the cholesterol ester of PFA. Reaction of the triesters with phosphorous pentachloride, followed by coupling with AZT and O-demethylation with sodium iodide, afforded 3'-azido-3'-deoxy-5'-O-[[(1-octadecyloxy)carbonyl]phosphinyl ]thymidine (9a), 3'-azido-3'-deoxy-5'-O-[[(1-eicosanyloxy)carbonyl]phosphinyl ]thymidine (9b), 3'-azido-3'-deoxy-5'-O-[[(1-docosanyloxy)carbonyl]phosphinyl ]thymidine (9c), and 3'-azido-3'-deoxy-5'-O-[[(3 beta-cholest-5-enyloxy)carbonyl]phosphinyl]thymidine (9d). Concentrations of 9a-d found to inhibit replication of wild-type HIV-1LAI by 50% (EC50 values) as measured in a plaque reduction assay were in the 0.1-0.3 microM range as compared with 0.013 microM for AZT and 133 microM for PFA. The concentration at which toxicity was observed in 50% of the host cells (TC50 values) as measured by a visual grading scale of cellular morphology was 10 microM for 9a and 9d, 32 microM for 9b, and 320 microM for 9c. Thus, the TC50/EC50 ratio or selectivity index (SI) was 100 for 9a, 230 for 9b, and 1000 for 9c but only 33 for 9d, suggesting that the straight-chained fatty alcohol esters were more therapeutically selective. Similar TC50 and SI values were obtained for rapidly dividing CEM lymphoblasts as for HT4-6C cells. In assays against E89K, 9a-c had mean EC50 values of 0.13, 0.009, and 0.17 microM, whereas the EC50 of PFA was > 1000 microM and that of AZT was 0.009 microM; thus, E89K was highly resistant to PFA but not cross-resistant to either AZT or the lipophilic PFA-AZT conjugates. In viral replication assays against the A018C-post isolate, the mean EC50 values of 9a-c were 0.30, 0.53, and 0.77 microM as compared with 2.9 microM for AZT and 65 microM for PFA; thus, the virus recovered from a patient pretreated with AZT was not cross-resistant to either PFA or 9a-c. A notable feature of these results was that, in addition to being > 1000-fold more potent than PFA against the PFA-resistant mutant, the lipophilic PFA-AZT conjugates were more potent than PFA, as well as AZT, against AZT-resistant HIV-1.

Subxiphoid pericardial window for pericardial effusion in end-stage renal disease

Fifty-seven patients with end-stage renal disease who were on maintenance dialysis underwent pericardial fluid drainage surgically between January 1980 and December 1991. All patients had echocardiographically proven pericardial effusion of more than 300 to 500 mL. Seven patients had pericardiectomy by left thoracotomy under general anesthesia in the first 2 years. Subsequently, 50 patients underwent a subxiphoid pericardial window by a left subcostal incision. A pericardial drainage tube was inserted at surgery and removed after 4 to 5 days. All but five patients undergoing subxiphoid pericardial window surgery received local anesthesia. The xiphoid process was not resected during surgery and steroids were not instilled in the pericardial cavity. There were minimal complications, no surgery-related deaths, and no recurrence of fluid in patients after pericardial window surgery. With our present experience, we advise a subxiphoid pericardial window with pericardial drainage under local anesthesia for all end-stage renal disease patients on dialysis who have a symptomatic or large pericardial effusion of more than 300 to 500 mL. Steroid instillation is not necessary for the prevention of recurrence of effusion.

Inhibition of phagocytes by cyclosporin in vitro

Cyclosporin is an immunosuppressant that acts by selectively inhibiting the activation of T lymphocytes. Its effects on monocytes and neutrophils are not well explored. We investigated the in vitro effects of cyclosporin on these cells, harvested from venous blood from nine healthy, non-smoking volunteers. In vitro incubation of monocytes with increasing concentrations of cyclosporin (5, 25 and 625 micrograms) depressed their phagocytosis by 22%, 32% and 49%, respectively, compared to the control values. The intracellular killing capacity of monocytes decreased by 26%, 31% and 43% with these doses, and neutrophil phagocytosis was depressed in a similar manner (16%, 30% and 40%). Patients receiving cyclosporin are susceptible to infections, and inhibition of these phagocytic cells by cyclosporin may be partly responsible for this. Neutrophil chemotaxis is reduced in patients with impaired renal function. Treating these patients with cyclosporin may in addition suppress the phagocytic function of these cells.

Sediment cytology in bone biopsies

The cytologic examination of smears prepared from the sediment of biopsy specimen fixatives ("sediment cytology") was used to study 70 bone lesions biopsied with a suspicion of malignancy. The smears were adequately cellular in most cases and showed good morphologic preservation; some contained fragments of tissue. Cytology was able to identify the smears from the 47 malignant lesions as malignant, but was not always able to identify the histologic type. While the osteoclastomas, Ewing's sarcomas and metastatic carcinomas were accurately diagnosed, the osteogenic sarcomas could only be identified as sarcomas and the scanty smears from chondrosarcomas only permitted a diagnosis of malignancy. The latter was also true for soft tissue lesions and lymphoma involving the bones. The 12 benign lesions yielded less cellular specimens and were more difficult to cytologically diagnose. The 11 inflammatory lesions were identified as nonmalignant. While this simple technique of sediment cytology can provide an early diagnosis for bone lesions, the final diagnosis requires the histopathologic study of the actual biopsy specimen.

Pulmonary tumor embolization after peritoneovenous shunting for malignant ascites

An 85-year-old woman with intractable malignant ascites secondary to ovarian carcinoma underwent peritoneovenous shunting (Denver shunt) in an attempt to alleviate the ascites. Implantation of the shunt resulted in massive embolization of tumor cells to the pulmonary vasculature. Postoperatively, she developed increasing hypoxia with progressive rises in pulmonary artery pressure, and died 48 hours after surgery as a result of occlusion of the pulmonary vascular bed by tumor emboli. This is the sixth reported instance of massive tumor embolization to the pulmonary circulation in patients with peritoneovenous shunting for malignant ascites.

Gunshot wound of the left chest and Bochdalek hernia

A 16-year-old male presented with a hemopneumothorax following a gunshot wound to the left chest. He was treated effectively with closed suction drainage for 48 hours when he suddenly complained of severe left chest pain. Preoperative diagnosis was suggestive of a traumatic diaphragmatic hernia but operative findings were confirmatory of a rare hernia through the foramen of Bochdalek. Chest X-ray showing a gas-filled viscus above the diaphragm is diagnostic. Increased abdominal pressure generated when he was first hit by the bullet and aggravated by increased negative intrapleural pressure resulting from suction drainage of the hemothorax is the probable mechanism of the herniation.

Hemoperitoneum from ruptured omental varices

We report a patient with hemoperitoneum from rupture of intraperitoneal varices. Hemoperitoneum is rare. Nevertheless, it should be easily recognized in a patient with abdominal pain and distension, a falling hematocrit in the absence of external blood loss, and gross blood in the abdominal fluid. The syndrome is another justification for early paracentesis in patients with abdominal fluid. Mortality remains high despite surgical correction of the bleeding and reflects the severity of the underlying liver disorder.