The influence of the visual cortex on the spatiotemporal response properties of lateral geniculate nucleus cells

Previous studies of the cortical input to the mammalian dorsal lateral geniculate nucleus (LGN) have identified a number of possible functions for the corticogeniculate pathway, including alteration of LGN spatial frequency selectivity and facilitation of both binocular interactions and orientation selectivity. These changes may be due to either a tonic or a phasic cortical facilitation or both. The temporal differences between each of these inputs suggests that their impact on LGN cell temporal tuning should be unique. To test this hypothesis, we reversibly blocked the visual cortex (VI) and measured the effects on several indices of the temporal properties of LGN cells, including peak frequency, bandwidth, and response phase. Macaque monkeys were anesthetized and paralyzed during single cell recording from the LGN while area VI was cryogenically deactivated. Single-cell responses were visually evoked with drifting, luminance-modulated, sine-wave gratings and discrete-Fourier analyzed. Cortical cooling produced statistically significant increases or decreases in response amplitude in 64% of cells recorded. In most cases, alterations in response amplitude occurred for stimuli that varied in spatial as well as temporal frequency. For those cells influenced by changes in stimulus temporal frequency, the majority showed changes over a broad range of frequencies. A minority of cells showed changes in either peak temporal tuning or temporal frequency bandwidth. Response phase angles for all temporal frequencies tested were unaffected by cortical cooling. Overall, these results suggest that the cortical input may alter the temporal response properties of LGN cells, perhaps by tonic, but not exclusively excitatory, corticofugal influences.     

Treatment of hepatocellular carcinoma associated with cirrhosis in the era of liver transplantation

PURPOSE: To review the treatment of cirrhotic patients with hepatocellular carcinoma in the era of liver transplantation and to determine the most appropriate approach to the treatment of patients at different stages of disease. DATA SOURCES: A MEDLINE search of English-language articles published between 1981 and 1997 and the clinical experience of the Mount Sinai Liver Transplant Program. STUDY SELECTION: Selected studies were 1) original articles reporting results of resection and transplantation in the treatment of hepatocellular carcinoma in cirrhotic patients and 2) initial reports from major transplantation centers of multimethod therapies combining chemotherapy with transplantation. DATA EXTRACTION: Study designs were assessed with careful attention to methods and aims. Relevant data on patient population, tumor stage distribution, treatment, survival, and rate of recurrent disease were extracted and analyzed. DATA SYNTHESIS: Options for the treatment of hepatocellular carcinoma in cirrhotic patients vary according to tumor stage and severity of underlying liver disease. Resection remains an important method primarily in eastern countries, where the screening of high-risk populations has been associated with early detection of small asymptomatic lesions. Long-term survival after resection, however, is low. In western countries, liver transplantation is becoming the treatment of choice in patients with advanced cirrhosis and small, unresectable lesions; resection is reserved for cirrhotic patients with small, peripheral lesions and preserved hepatic function. Minimally invasive procedures (such as percutaneous ethanol injection and transarterial chemoembolization) have been developed to treat unresectable tumors. Transarterial chemoembolization may also be effective in patients with advanced cirrhosis and unresectable lesions who are awaiting transplantation. CONCLUSIONS: The efficacy of liver transplantation for hepatocellular carcinoma has been proven mainly in patients with advanced cirrhosis and small lesions. Future studies may clarify the role of approaches combining neoadjuvant chemotherapy with transplantation for large (stage III) tumors.     

Laparoscopic splenectomy: outcome and efficacy in 103 consecutive patients

OBJECTIVE: To study the safety and efficacy of laparoscopic splenectomy (LS) in patients with predominantly benign hematologic disorders. SUMMARY BACKGROUND DATA: The technical feasibility of LS has been recently established. However, data regarding the efficacy of the procedure in a large cohort of patients are scarce. METHODS: One hundred three consecutive patients underwent LS between June 1992 and October 1997. Data were collected prospectively on all patients. RESULTS: Indications were idiopathic thrombocytopenic purpura (ITP), hereditary spherocytosis, autoimmune hemolytic anemia, thrombotic thrombocytopenic purpura, and others. Mean spleen size was 14 cm and mean weight was 263 g. Accessory spleens were found in 12 patients with ITP and in 5 patients without ITP. There were no deaths. Complications occurred in six patients, one requiring a second procedure for small bowel obstruction. Six patients received transfusions, and four procedures were converted to open splenectomy for bleeding. Mean surgical time was 161 minutes and was greater in the first 10 cases than the last 10. Mean postsurgical stay was 2.5 days. Thrombocytopenia resolved after surgery in 84% of patients with ITP, and hematocrit levels increased significantly in 70% of patients with chronic hemolytic anemias. A positive response was noted in 92% of patients with hereditary spherocytosis, without relapse for the duration of the observation. ITP relapsed in four patients during follow-up, three within 12 months. CONCLUSIONS: LS can be performed safely and effectively in a teaching institution. Rigorous technique will minimize capsular fractures, reducing the risk of splenosis. Accessory spleens can be successfully localized, thus improving response and limiting recurrence of ITP. LS should become the technique of choice for treatment of intractable benign hematologic disease.     

Interferon gamma protects against hepatic tumor growth in rats by increasing Kupffer cell tumoricidal activity

An increasing number of hepatic resections are being performed as potentially curative surgery for malignant liver neoplasms. Hepatectomy and subsequent liver regeneration produce a local environment that enhances growth of microscopic residual tumor. To determine if pretreatment with murine interferon gamma (IFN-gamma) can protect against such enhanced tumor growth, Buffalo rats were randomized to receive a 3-day treatment of IFN-gamma (50,000 U/qD intraperitoneally) or saline. Groups then underwent intrasplenic injection of 10(6) Morris hepatoma cells, followed 1 hour later by sham (control) or partial hepatectomy (PH) of 70%. PH significantly enhanced tumor growth within the liver (control, 8 +/- 3 nodules per liver; PH, 73 +/- 12 nodules per liver; P < .001). This enhancement was attenuated by prior administration of IFN-gamma IFN-gamma/PH, 16 +/- 3; P < .001 vs. PH). Growth factor release and liver regeneration were not affected significantly by pretreatment with IFN-gamma. The effect of IFN-gamma on tumor growth is associated with a significant enhancement of Kupffer cell (KC)-mediated tumoricidal activity (percentage of specific lysis, 55 +/- 10% control, 78 +/- 11% IFN-gamma, P < .01) but not lymphocyte-mediated tumoricidal activity. Because microscopic residual disease may be present after hepatectomies for cancer, IFN-gamma may be useful agent in retarding growth of residual tumors.     

Evaluation of anti-nociceptive effects of neuronal nicotinic acetylcholine receptor (NAChR) ligands in the rat tail-flick assay

In the present investigation, anti-nociceptive effects of neuronal nicotinic acetylcholine receptor (NAChR) ligands, (+)- and (-)-nicotine, cytisine, methylcarbamylcholine (MCC), dimethylphenylpiperazinium iodide (DMPP), and (+/-)-epibatidine were evaluated in the rat tail-flick assay both after subcutaneous (s.c.) and intracerebroventricular (i.c.v.) administration. The pharmacology of the tail-flick response to NAChR ligands after s.c. and i.c.v. routes was similar. Epibatidine was the most potent ligand examined with a longer duration of action than any other agonist. (-)-Nicotine was more active than (+)-nicotine indicating stereospecificity. ICV administration studies indicated an apparent partial agonist activity for (+)-nicotine in the tail-flick response. Tail-flick responses to NAChR agonists are independent of opioid and muscarinic pathways and appear to be mediated both by central and peripheral NAChR recognition sites. Central administration of MCC activates both NAChR and muscarinic anti-nociceptive mechanisms. Studies employing the alpha-adrenergic receptor alkylating agent, phenoxybenzamine or the noradrenergic neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), suggested that the NAChR-noradrenergic and NAChR-serotoninergic interactions play an important role in the tail-flick response. Studies employing a selective alpha-bungarotoxin-sensitive NAChR receptor antagonist, methyllycaconitine (MLA), suggested a minimal role for these receptors in the tail-flick response. The biochemical studies also indicated that a sub-population of NAChR receptors are located pre-synaptically on noradrenergic and/or serotoninergic pathways in the hippocampus.     

A clinicopathologic study of mucinous gastric carcinoma including multivariate analysis

BACKGROUND: Mucinous gastric carcinoma (MGC) is a rare subtype of gastric adenocarcinoma, and its clinical and pathologic features are still controversial. To clarify the significance of this subtype of carcinoma, the authors conducted a case-control study to investigate the clinicopathologic characteristics of MGC and determine whether this mucin-producing histologic type is associated with a worse prognosis than other gastric carcinomas. METHODS: Twenty-two cases of MGC and 46 patients with nonmucinous gastric carcinoma (NGC) were included. Patients were evaluated on the basis of age, gender, tumor size, location, depth of tumor invasion, histologic differentiation, lymph node involvement, organ metastasis, stage at presentation, surgical curability, adjuvant chemotherapy and radiation therapy. To determine whether the MGC itself was an independent prognostic factor, a multivariate analysis was performed with the Cox proportional hazards model. RESULTS: The MGC patients were found to have larger tumors (P < 0.001), tumors more often located in the upper stomach (P < 0.05), more serosal invasion (P < 0.05), more lymph node involvement (P < 0.05), greater frequency of advanced stage disease (P < 0.01), and lower 5-year survival rates (P < 0.05) than NGC patients. There was no significant correlation between the subtypes of differentiation of MGC and other data, including the prognosis. Multivariate analysis showed that clinically important predictive factors were serosal invasion and disease stage at diagnosis. The mucinous histologic type itself was not an independent factor for poor prognosis. CONCLUSIONS: The overall survival rate for patients with MGC was worse than that for patients with NGC. The poor prognosis was correlated with more advanced stage at diagnosis and more frequent serosal invasion, not with the mucinous histologic type.     

Effects of albumin and/or furosemide therapy on pulmonary edema induced by hydrochloric acid aspiration in rabbits

Aspiration of hydrochloric acid in rabbits resulted in an increased P(A-a)O2 together with increases in both lung water volume and lung extravascular albumin. This finding suggests lung damage following acid aspiration is related to changes in capillary permeability, with pulmonary edema resulting from the movement of albumin and water into the interstitial space. Therapy with albumin and furosemide together reduced the lung water and albumin accumulation and decreased P(A-a)O2. Treatment with albumin or furosemide alone was ineffective. Caution should be exercised in administering albumin alone for therapy of pulmonary edema when plasma protein is not clearly decreased, or when increased pulmonary capillary permeability is suspected.     

Tremorogenic effects of intracaudate d-amphetamine and their suppression by dopamine

Pronounced tremors were produced in unanesthetized cats following intracaudate (I.C.) injections of either d-amphetamine (15 mug), dl-methamphetamine (20 mug), l-amphetamine (48 mug) or 3-methoxytyramine (68-120 mug). Yet, a series of other chemically and pharmacologically related phenylethylamines, including dopamine (90 mug), were not tremorogenic even at substantially higher doses. The d-amphetamine tremors developed rapidly, failed to exhibit tachyphylaxis to repeated challenging doses (15 mug) and were not influenced by pretreatment with alpha-methyl-p-tyrosine. They also developed independently of local acetylcholine activity as evidenced by the inability of cholinergic antagonists (scopolamine and hemicholinium) to interfere with the tremors. Significant qualitative differences were found between the I.C. effects of d-amphetamine (15 mug) and dopamine (15-90 mug): d-amphetamine further increased the intensity of ongoing tremors induced by physostigmine (111 mug I.C.), whereas, dopamine readily inhibited the latter. When superimposed, I.C. dopamine was equally effective in suppressing d-amphetamine tremor activity. The results emphasize the selective tremorogenic actions of d-amphetamine and call attention to the contrasting stabilizing role of dopamine. This would suggest that two types of adrenergic receptor sites are operative in the caudate in neuroregulation of involuntary movements.     

Flaujeac factor deficiency. Reconstitution with highly purified bovine high molecular weight-kininogen and delineation of a new permeability-enhancing peptide released by plasma kallikrein from bovine high molecular weight-kininogen

Flaujeac trait is the functional deficiency of a plasma protein of the intrinsic coagulation, kinin-forming, and plasma fibrinolytic pathways. The Flaujeac factor in man has been isolated and tentatively identified as a kininogen of high molecular weight (HMW). Highly purified bovine HMW-kininogen, but not bovine low molecular weight kininogen, repaired Flaujeac factor deficiency. The two subspecies of this molecule, HMW-kininogen a and HMW-kininogen b, also corrected Flaujeac factor deficiency. When bovine HMW-kininogen was incubated with bovine plasma kallikrein, kinin-free HMW-kininogen, bradykinin, and a glycopeptide fragment (peptide 1-2; 12,584 daltons) were rapidly released. None of these fragmentation products corrected Flaujeac factor deficiency alone or in mixtures. The function of HMW-kininogen appeared to depend upon the structural integrity of the native molecule. When injected in concentrations of 2 pmol-8 nmol/0.1 ml, peptide 1-2 caused increased vascular permeability in rabbits, rats, or guinea pigs. The enhanced permeability was maximal within 1-2 min and terminated in 5-10 min, differing from that of bradykinin or histamine. Injected together in equimolar amounts, peptide 1-2 and bradykinin produced a synergistic permeability response which was immediate in onset as well as prolonged in duration. Peptide 1-2 is a rapidly acting, highly basic glyco-peptide which mediates increased vascular permeability in a complementary and synergistic manner with bradykinin.     

Reliability of A Tree Network

This paper presents a mathematical model for computing the reliability of a system with redundant components in a tree configuration. This model is quite general and can be applied to any system representable by the appropriate tree. A typical example is cited. A computer program that computes reliability of a system with a tree configuration up to n stages is also presented in the Appendix.