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.

Laparoscopic management of complications of peptic ulcer disease.

Laparoscopic treatment of intractable duodenal ulcers is intended for the treatment of patients who do not heal after a trial of intensive regimen of medication such as H2 blockers and/or therapy aimed at eradication of Helicobacter pylori. Patients in a category who are Helicobacter-negative can be offered a laparoscopic treatment of their ulcer by vagotomy. Patients who have early relapses on stopping medical treatment are also candidates for vagotomy. Complications of the disease, such as bleeding or pyloric outlet obstruction, represent valid indications in 1995 for performing surgery in patients with duodenal ulcer disease.

Laparoscopic splenectomy.

Several indications for laparoscopic splenectomy are represented mainly by hematological disorders such as Idiopatic Thrombopenic Purpura (ITP) or hereditary spherocytosis. Patients with ITP who do not respond, have relapses of the disease under steroid treatment, or need a gradually increased dose of steroids, represent an excellent indication for laparoscopic splenectomy, as the spleen is not enlarged. Patients are usually small, thin, young females, making the procedure much easier. The size of the spleen in hereditary spherocytosis varies, sometimes making the procedure a little more difficult, especially as those patients have pigmented gallbladder stones necessitating a concurrent laparoscopic cholecystectomy. Other indications are represented by staging of Hodgkin's disease, lymphoma of the spleen, and splenic infarcts without abscesses. Some patients with autoimmune hemolytic anemia might benefit from laparoscopic splenectomy, but hypersplenism due to cirrhosis is strongly contraindicated, as the risk of intraoperative hemorrhage is great and not usually managed easily laparoscopically.

Subtotal splenectomy for Gaucher's disease: a follow-up study.

Three patients with Gaucher's disease who underwent partial splenectomy have been followed for 3, 7 3/4, and 8 1/2 years. All have had significant regrowth of the the splenic remnant and some recurrence of hypersplenism. A review of all previously reported cases also substantiates the recurrence of splenomegaly and hypersplenism. Among new options for the therapy of Gaucher's disease, enzyme replacement therapy (Ceredase) holds great promise for effective treatment.

The clinical spectrum of lymphangiomas and lymphangiomatosis of the spleen.

Lymphangiomas of the spleen are infrequent neoplasms of the spleen with clinical manifestations ranging from insignificant incidental findings to large, symptomatic cystic masses requiring surgical intervention. An associated syndrome may be lymphangiomatosis, in which the lymphangiomatous process involves other sites or organs, such as the liver, spleen, axilla, and mediastinum. Vasoformative neoplasms (hemangioma, lymphangioma) are relatively uncommon tumors or hamartomas of the spleen. Although well reported in the literature, their surgical significance is not well recognized. These lesions present a broad spectrum of pathologic findings of varied surgical importance. As incidental findings, they may be mistakenly considered as a valid indication for splenectomy. On the contrary, more extensive involvement of the spleen may cause symptomatic splenomegaly, which is a valid indication for splenectomy. When the spleen is diffusely involved (lymphangiomatosis), it may be part of a syndrome of generalized lymphangiomatosis involving structures and organs other than the spleen. This syndrome should be considered in obscure cases of splenomegaly in which the usual hematologic causes have been ruled out.

Purification, characterization, and kinetic analysis of inosine 5'-monophosphate dehydrogenase of Tritrichomonas foetus.

The IMP dehydrogenase of Tritrichomonas foetus, a parasitic protozoan incapable of de novo biosynthesis of purine nucleotides, has been purified about 1000-fold to apparent homogeneity. The purified enzyme demonstrated a 20-fold higher substrate turnover rate than the pure IMP dehydrogenase from sarcoma ascites tumor cells. It has a subunit molecular weight of 58,000, aggregates to a size of 380,000 at low ionic strength, and partly dissociates to a molecular weight of 270,000 in high salt concentrations. Unlike the IMP dehydrogenase of bacteria and mammals, the T. foetus enzyme does not require K+ for activity. The analysis of initial velocity and product inhibition data is consistent with a sequential, ordered bi bi kinetic mechanism for the parasite enzyme-catalyzed reaction, in which IMP binds before NAD+ and NADH is released before XMP. This is in contrast to the partially random mechanism of the bacterial enzyme which involves the formation of an enzyme-K+-(IMP) complex. Mycophenolic acid inhibits T. foetus IMP dehydrogenase uncompetitively versus both IMP and NAD+ with an apparent Ki of 9 microM. This value, which is several hundred-fold higher than that for mammalian IMP dehydrogenase, suggests significantly different binding properties of the mycophenolic acid site in T. foetus IMP dehydrogenase, which might be amenable to specific inhibitor design.

Differential effects of inhibitors of purine metabolism on two trichomonad species.

Tritrichomonas foetus and Trichomonas vaginalis are both incapable of de novo purine nucleotide synthesis. Previous studies indicated that T. foetus relies mainly on the salvage of hypoxanthine and subsequent conversion of IMP to AMP and GMP, whereas T. vaginalis depends on direct conversions of exogenous adenosine to AMP and guanosine to GMP without much interconversion between the two nucleotides. These two different types of purine salvage suggest the possibility of differential sensitivities between the two species of trichomonad flagellates toward different purine antimetabolites. Mycophenolic acid, hadacidin, 8-azaguanine, and formycin B inhibited the growth of T. foetus but had no effect on T. vaginalis. Mycophenolic acid acted by blocking conversion of IMP to GMP, hadacidin inhibited conversion of IMP to AMP, and 8-azaguanine was incorporated into the T. foetus nucleotide pool, likely via hypoxanthine phosphoribosyl transferase. Formycin B was converted to 5'-monophosphate in T. foetus and inhibited the conversion of IMP to AMP. Its precise mechanism of action on T. foetus remains, however, to be elucidated. Alanosine, whose ribonucleotide derivative is a potent inhibitor of adenylosuccinate synthetase, had no effect on the growth or hypoxanthine incorporation in T. foetus, which may be due to the lack of conversion of alanosine to the ribonucleotide because of the absence of de novo purine nucleotide synthesis in parasites. Four adenosine analogs, adenine arabinoside, tubercidin, sangivamycin, and toyocamycin, were found inhibitory to the growth of T. vaginalis but showed little effect on T. foetus growth. Further investigations suggested that these four compounds acted on T. vaginalis by blocking incorporation of adenosine into the adenine nucleotide pool.

Purine salvage by Tritrichomonas foetus.

The anaerobic protozoon Tritrichomonas foetus was found incapable of de novo purine synthesis by its failure to incorporate radiolabeled glycine or formate into the nucleotide pool. It had, on the other hand, high activities in incorporating adenine, hypoxanthine or inosine. Radiolabel pulse-chase experiments indicated that adenine, hypoxanthine and inosine all entered the pool through conversion to IMP. The parasite contained hypoxanthine phosphoribosyl transferase, adenine deaminase and inosine phosphorylase, but no adenine phosphoribosyl transferase, inosine kinase or inosine phosphotransferase activity. Adenine and inosine had to be converted to hypoxanthine before incorporation. Adenosine was also rapidly converted to hypoxanthine in T. foetus cell-free extracts, but the presence of adenosine kinase in the parasite allowed some conversion of adenosine directly to AMP. Guanine and xanthine were directly incorporated into GMP and XMP, probably due to the guanine and xanthine phosphoribosyl transferase. There were also strong enzyme activities which convert guanosine to guanine and guanine to xanthine. A guanosine phosphotransferase was found in the 10(5) X g sedimentable fraction of T. foetus, and was capable of converting some guanosine to GMP. This network of T. foetus purine salvage suggests the importance of hypoxanthine-guanine-xanthine phosphoribosyl transferase activities in the parasite.

Pyrimidine metabolism in Tritrichomonas foetus.

The anaerobic parasitic protozoa Tritrichomonas foetus is found incapable of de novo pyrimidine biosynthesis by its failure to incorporate bicarbonate, aspartate, or orotate into pyrimidine nucleotides or nucleic acids. Uracil phosphoribosyltransferase in the cytoplasm provides the major pyrimidine salvage for the parasite. Exogenous uridine and cytidine are mostly converted to uracil by uridine phosphorylase and cytidine deaminase in T. foetus prior to incorporation. T. foetus cannot incorporate labels from exogenous uracil or uridine into DNA; it has no detectable dihydrofolate reductase or thymidylate synthetase and is resistant to methotrexate, pyrimethamine, trimethoprim, and 5-bromovinyldeoxyuridine at millimolar concentrations. It has an enzyme thymidine phosphotransferase in cellular fraction pelleting at 100,000 X g that can convert exogenous thymidine to TMP via a phosphate donor such as p-nitrophenyl phosphate or nucleoside 5'-monophosphate. Thymidine salvage in T. foetus is thus totally dissociated from other pyrimidine salvage.