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Biomedical subjects

A L Hoffman

Publications and source records attributed to A L Hoffman.

At least 19 recordsLinked to original sources
PubMed2005

Observations of improved stability and confinement in a high-beta self-organized spherical-torus-like field-reversed configuration.

An extremely high-beta (over 85%) self-organized field-reversed configuration (FRC) with a spherical-torus- (ST-)like core is produced in the translation, confinement, and sustainment experiment by highly super-Alfvénic translation of a spheromaklike plasmoid. Substantial flux conversion from toroidal into poloidal occurs during the capture process, resulting in the ST-like core. This plasma state exhibits a remarkable stabilizing property for the ubiquitous centrifugally driven interchange modes present in theta-pinch formed FRCs. This is explained, for the first time, by a simple model taking into account magnetic shear and centrifugal effects. The FRC-ST configuration has up to 4 times improvement in flux confinement times over the scaling of conventional theta-pinch formed FRCs and, thus, a significant improvement in the resistivity and transport.

Journal Article↗
PubMed2005

Stabilization of interchange modes by rotating magnetic fields.

Interchange modes have been a key limiting instability for many magnetic confinement fusion configurations. In previous studies intended to deal with these ubiquitous instabilities, complex, transport enhancing, minimum-B producing coils were added to the otherwise simple linear mirror plasma. Possible solutions for returning to a simple symmetric mirror configuration, such as ponderomotive fields, are weak and difficult to apply. A new method is demonstrated here for the first time, utilizing rotating magnetic fields that are simple to apply and highly effective. A simple and easily comprehensible theory has also been developed to explain the remarkable stabilizing properties. Although this work has been performed on field reversed configurations, it should have a wide application to other confinement schemes, and could become a cornerstone for high-beta plasma stability.

Journal Article↗
PubMed2004

Flux conversion and evidence of relaxation in a high-beta plasma formed by high-speed injection into a mirror confinement structure.

High-beta plasmoids can survive the violent dynamics of supersonic reflection off mirror structures, producing a stable high-beta field-reversed configuration (FRC). This shows both the robustness of FRCs and their tendency to assume a preferred plasma state, possibly conforming to a relaxation principle. The key observations are (1) approximate preservation of the magnetic helicity, (2) substantial conversion from toroidal to poloidal magnetic flux, (3) substantial toroidal flow, and (4) a high-beta quiescent final state. These results are from the Translation, Confinement, and Sustainment experiment where a disorganized plasmoid is injected at super-Alfvenic speed into a confinement chamber. After successive reflections from end mirrors, the plasmoid settled into a near-FRC state with high beta and low toroidal magnetic field. The flux conversion and helicity preservation are inferred by an interpretive model.

Journal Article↗
PubMed2001

Long-term results of metallic stents for benign biliary strictures.

BACKGROUND: Historically, surgical correction has been the treatment of choice for benign biliary strictures (BBS). Self-expandable metallic stents (MSs) have been useful for inoperable malignant biliary strictures; however, their use for BBS is controversial and their natural history unknown. HYPOTHESIS: To test our hypothesis that MSs provide only short-term benefit, we examined the long-term outcome of MSs for the treatment of BBS. Our goal was to develop a rational approach for treating BBS. DATA EXTRACTION: Between July 1990 and December 1995, 15 patients had MSs placed for BBS and have been followed up for a mean of 86.3 months (range, 55-120 months). The mean age of the patients was 66.6 years and 12 were women. Stents were placed for surgical injury in 5 patients and underlying disease in 10 patients (lithiasis, 7; pancreatitis, 2; and primary sclerosing cholangitis, 1). One or more MSs (Gianturco-Rosch "Z" for 4 patients and Wallstents for 11 patients) were placed by percutaneous, endoscopic, or combined approaches. We considered patients to have a good clinical outcome if the stent remained patent, they required 2 or fewer invasive interventions, and they had no biliary dilation on subsequent imaging. DATA SYNTHESIS: Metallic stents were successfully placed in all 15 patients, and the mean patency rate was 30.6 months (range, 7-120 months). Five patients (33%) had a good clinical result with stent patency from 55 to 120 months. Ten patients (67%) required more than 2 radiologic and/or endoscopic procedures for recurrent cholangitis and/or obstruction (range, 7-120 months). Five of the 10 patients developed complete stent obstruction at 8, 9, 10, 15, and 120 months and underwent surgical removal of the stent and bilioenteric anastomosis. Four of these 5 patients had strictures from surgical injuries. The patient who had surgical removal 10 years after MS placement developed cholangiocarcinoma. CONCLUSIONS: Surgical repair remains the treatment of choice for BBS. Metallic stents should only be considered for poor surgical candidates, intrahepatic biliary strictures, or failed attempts at surgical repair. Most patients with MSs will develop recurrent cholangitis or stent obstruction and require intervention. Chronic inflammation and obstruction may predispose the patient to cholangiocarcinoma.

Adult↗
PubMed1999

Metastasis of hepatocellular carcinoma to the right colon manifested by gastrointestinal bleeding.

An 82-year-old black woman with a history of hepatocellular carcinoma presented with gastrointestinal bleeding. Barium enema and fibrocolonoscopy revealed a 4-cm polypoid mass at the level of the ascending colon with evidence of active bleeding. Biopsies of the lesion proved it to be metastatic hepatocellular carcinoma. Exploratory laparotomy revealed no further dissemination of the tumor, and the patient underwent an ileocolectomy. The serosal side of the colonic lesion was free from tumor, and there was no peritoneal implantation, direct extension, or lymph node involvement. This case represents an extremely rare presentation of metastatic hepatocellular carcinoma.

Aged↗
PubMed1997

Hepatic angiomyolipoma: two case reports of caudate-based lesions and review of the literature.

Two case reports of hepatic angiomyolipoma, both originating in the caudate lobe, are reported with a review of the literature. The liver is the second most common site of angiomyolipoma, an uncommon benign tumor of mixed mesenchymal origin. It is commonly diagnosed following abdominal pain or as an asymptomatic mass discovered on abdominal ultrasound or computed tomography scan. Of 74 cases reported, the lesions ranged from 0.3 to 36 cm in diameter and are noted between the first and eighth decade, with predominant female predilection. The right lobe is the most common site, with lesions arising in the caudate lobe comprising only five cases. The natural history of the hepatic lesion is unknown. Malignant invasion or metastatic disease has not been documented. Hepatic and renal angiomyolipoma can occur concurrently (13 of 60 cases), although the majority are not biopsy proven. Multicentric hepatic disease occurs. The correlation between tuberous sclerosis and hepatic angiomyolipoma is not confirmed histologically and occurs rarely. These lesions have a characteristic radiographic appearance due to high fat content. Histologically, angiomyolipoma are characterized by an admixture of adipose tissue, blood vessels, and smooth muscle cells. These lesions cannot reliably be differentiated from a malignant lesion based on clinical history, radiologic examination, and/or pathologic interpretation. If clinical suspicion for malignancy is low, then careful observation with serial radiologic follow-up is performed. The treatment for a symptomatic or suspicious lesion is resection, if feasible. Liver transplantation may be considered for large or centrally located lesions not amenable to resection.

Adult↗
PubMed1997

Transarterial chemoembolization is a safe treatment for unresectable hepatic malignancies.

Acute liver failure has been reported as a frequent complication of transarterial chemoembolization (TACE). We prospectively evaluated the adverse effects and biochemical changes of TACE. From 10/95 to 9/96, 35 patients with hepatic malignancies were evaluated for TACE. Fifteen patients (9 male and 6 female) received 23 treatments. Ten of 15 patients had hepatocellular carcinoma, and 5 had metastatic tumors. Treatment exclusion criteria included advanced liver disease, hepatic vascular thrombosis, and severe comorbidity. TACE consisted of intra-arterial infusion of a mixture of doxorubicin, cisplatin, and mitomycin followed by embolization. Clinical symptoms and laboratory studies were monitored following treatment. Technical success was achieved in all patients. Adverse symptoms were transient, and most resolved within 1 week. Changes in hepatic, renal, and hematologic function were temporary and returned to pre-TACE levels by 1 month. None developed acute liver failure. The mean hospital stay was 3 days. Ten of 13 patients had a significant decrease in baseline tumor markers. The actual survival was 93 per cent with a median follow-up of 10 months. TACE can be performed safely in patients with hepatic tumors. The adverse effects can be anticipated and easily managed.

Adult↗
PubMed1996

Transjugular intrahepatic portosystemic shunt: efficacy for the treatment of portal hypertension and impact on liver transplantation.

Variceal bleeding (VB) and ascites refractory to diuretics (RA) represent a significant cause of morbidity and mortality in patients with portal hypertension. Transjugular intrahepatic portosystemic shunts (TIPS) have been used effectively in patients with these complications, especially those individuals awaiting orthotopic liver transplantation (OLT). From April 1992 to July 1995, 41 adult patients underwent an attempt at TIPS placement for refractory VB or ascites at Cedars-Sinai Medical Center. Technical success was achieved in 37 of 41 cases (90.3%) with only two technical complications. Immediate control of hemorrhage and significant improvement of ascites was obtained in 91.9% and 83.5% of the patients, respectively. Six patients (16.2%) died within a week of TIPS placement due to uncontrollable ascites and multiorgan failure. Four of 31 patients (12.9%) developed mild to moderate grades of hepatic encephalopathy that was controlled with lactulose. Rebleeding from recurrent portal hypertension was noted in 5 of 31 cases (16.1%). Shunt stenosis or occlusion was seen in 7 of 31 cases (22.6%) at an average of 6.3 months following TIPS placement. Six patients underwent OLT within an average of 87 days after TIPS. These results indicate that TIPS appears to be an effective method for treatment of refractory VB and RA, especially for patients who are poor candidates for a surgical shunt or awaiting OLT. However, TIPS may not be considered a definitive solution for all patients with portal hypertension because of its current rate of shunt occlusion or stenosis.

Adult↗
PubMed1995

Nicotine addiction counseling for chemically dependent patients.

A total of 771 professionals employed in alcohol treatment programs in Nebraska were surveyed to determine whether their personal alcohol and tobacco use status or characteristics of their treatment programs were related to whether they provided nicotine addiction counseling. About a third of respondents agreed that clients in active treatment should be urged to quit smoking. Compared with respondents who had never smoked, current smokers were one-half to one-third as likely to provide such counseling. Greater knowledge of the effects of nicotine addiction and employment in programs that provided nicotine addiction education or treatment increased the odds of counselors' providing nicotine counseling. Counselors' alcohol use status was not associated with nicotine counseling practices.

Adult↗
PubMed1995

Hepatic resection for malignancy in the elderly.

Although elderly patients are accounted for in all large series of major hepatic resections, the role of age as a determinant of outcome remains unclear. At Cedars-Sinai Medical Center, we review a series of 20 major hepatectomies for neoplasia performed in patients older than 66 years of age (4 of them > or = 80 years old) over a 5-year period. A retrospective comparison was conducted with a group of 22 hepatectomies for malignancy performed in 20 patients younger than 59 years of age during the same time period. The younger group had a significantly greater degree of liver resected (12 trisegmentectomies vs 3). Although one operative death (5% mortality) was observed in the elderly group, no statistically significant difference was noted, when compared to the younger group (Chi-square, P = 0.48). Likewise, no significant difference in the complication rate (20% vs 33%) was noticed (Chi-square, P = 0.8). Severe postoperative liver dysfunction was present in 2 cases (10%) in the elderly group and one (4%) in the younger group. These patients underwent a right trisegmentectomy (TS). Nine patients from each group were resected without red blood cell transfusion. We conclude that major hepatic resection in elderly patients without severe comorbid disease is a safe procedure that is not associated with an increased perioperative morbidity or mortality rate.

Age Factors↗
PubMed1994

Hepatic regeneration: current concepts and clinical implications.

Liver regeneration occurs as a result of hepatic tissue loss or injury. The process of liver regeneration is carefully regulated in a controlled biologic scheme with closely interactive relationships between hormones, free neurotransmitters, and nutrients; protooncogenes; and polypeptide and glycolipid growth factors. These relationships are now being studied at the molecular and cellular levels and attempts are being made to reconstruct the complete intricate process. Although significant breakthroughs have occurred in understanding the effects and regulation of several subsystems (such as insulin and its receptors; TGF-alpha and TGF-beta; HGF and its receptors), the integral process remains a mystery. Improved comprehension of the regeneration process will lead to rational treatment algorithms for now dreaded hepatic diseases.

Growth Inhibitors↗
PubMed1993

An empirical description of phases of maintenance following treatment for alcohol dependence.

This article reports two longitudinal prospective studies conducted sequentially to describe participants' maintenance of abstinence experiences up to 36 months posttreatment. Study 1 reports responses of 102 subjects who maintained alcohol abstinence following treatment and who were assessed for duration and intensity of symptoms associated with postacute withdrawal at baseline, 3, 6, and 12 months. A decreasing linear trend of symptoms was found as time of alcohol abstinence increased. Study 2 obtained interview and survey data from 23 successful abstainers from Study 1 at 12, 18, and 36 months posttreatment to describe coping strategies, perceptions of relapse risk, extent and duration of "aftercare," and substitute addictions as these phenomena developed and changed over time. Multiple occasions of data collection supported the description of three phases of maintenance: symptom stabilization/management accompanied by a cognitive paradigm shift, distancing self from alcohol-dependent behavior, and normalization of life processes.

Adult↗
PubMed1992

Theory and practice: bridging scientists' and practitioners' roles.

Past and recent progress in theory development for psychiatric mental health nursing (PMHN) and its link to practice are reviewed. Results of a national survey of practitioners reflecting the current use of theory from the disciplines of nursing, psychiatry, and behavioral sciences are reported. Progress addressed in furthering the science of PMHN includes the taxonomy of nursing diagnoses and concept analysis. Case study methods are acknowledged as one approach to continue theory development. One paradigm, representative case research (RCR), is noted for its heuristic value for theory development and its potential for bridging the scientist-practitioner roles of mental health clinicians.

Humans↗
PubMed1990

The use of FK-506 for small intestine allotransplantation. Inhibition of acute rejection and prevention of fatal graft-versus-host disease.

Small intestine allotransplantation in humans is not yet feasible due to the failure of the current methods of immunosuppression. FK-506, a powerful new immunosuppressive agent that is synergistic with cyclosporine, allows long-term survival of recipients of cardiac, renal, and hepatic allografts. This study compares the effects of FK-506 and cyclosporine on host survival, graft rejection, and graft-versus-host-disease in a rat small intestine transplantation model. Transplants between strongly histoincompatible ACI and Lewis (LEW) strain rats, and their F1 progeny are performed so that graft rejection alone is genetically permitted (F1----LEW) or GVHD alone permitted (LEW----F1) or that both immunologic processes are allowed to occur simultaneously (ACI----LEW). Specific doses of FK-506 result in prolonged graft and host survival in all genetic combinations tested. Furthermore, graft rejection is prevented (ACI----LEW model) or inhibited (rejection only model) and lethal acute GVHD is eliminated. Even at very high doses, cyclosporine did not prevent graft rejection or lethal GVHD, nor did it allow long-term survival of the intestinal graft or the host. Animals receiving low doses of cyclosporine have outcomes similar to the untreated control groups. No toxicity specific to FK-506 is noted, but earlier studies by other investigators suggest otherwise.

Animals↗
PubMed1989

Transplantation of multiple abdominal viscera.

Two children with the short-gut syndrome and secondary liver failure were treated with evisceration and transplantation en bloc of the stomach, small intestine, colon, pancreas, and liver. The first patient died perioperatively, but the second lived for more than 6 months before dying of an Epstein-Barr virus-associated lymphoproliferative disorder that caused biliary obstruction and lethal sepsis. There was never evidence of graft rejection or of graft-vs-host disease in the long-surviving child. The constituent organs of the homograft functioned and maintained their morphological integrity throughout the 193 days of survival.

Animals↗
PubMed1989

Immunomagnetic T-lymphocyte depletion (ITLD) of rat bone marrow using OX-19 monoclonal antibody.

Graft versus host disease (GVHD) may be abrogated and host survival prolonged by in vitro depletion of T lymphocytes from bone marrow (BM) prior to allotransplantation. Using a mouse anti-rat pan T-lymphocyte monoclonal antibody (OX19) bound to monosized, magnetic, polymer beads, T lymphocytes were removed in vitro from normal bone marrow. The removal of the T lymphocytes was confirmed by flow cytometry. Injection of the T-lymphocyte-depleted bone marrow into fully allogeneic rats prevents the induction of GVHD and prolongs host survival.

Animals↗