Detection of platelet-directed immunoglobin G in sera using the peroxidase-anti-peroxidase (PAP) slide technique

An immunohistochemical procedure for the detection of immunoglobulin G adherent to platelets is described. The peroxidase anti-peroxidase method is used to detect antibody activity directed against platelets from normal donors in the sera from 305 individuals. These subjects were divided into three groups: group 1, patients referred for tissue typing; group 2, healthy normal females; group 3, healthy normal males. In group 1, 28% of the sera were found to be positive; in most of these a history of prior transfusions was obtained. In group 2, 7.4% were found to be positive, most having previous pregnancies. Only 1% were found to be positive in group 3, and no reason for presensitization was found. Results from the indirect immunofluorescence technique served as a control and as a means to compare the sensitivity. Under the conditions chosen, the peroxidase anti-peroxidase test was two to eight times more sensitive than the immunofluorescence technique. Specificity of the peroxidase anti-peroxidase technique was demonstrated using a monospecific anti-PLA1 antiserum. It is concluded that the peroxidase anti-peroxidase slide technique may be a useful tool in the study of platelet-related immunophenomena.     

Human platelets exert cytotoxic effects on tumor cells

Monocytes are thought to play a role in host resistance to tumor cell growth in animals and humans. In addition, platelets are known to be involved in tumor metastases. To investigate the interaction of these two cell types and their effect on tumor cells, human monocytes and platelets were examined using an in vitro monocyte-tumor cell cytotoxicity assay. Monocytes alone resulted in 32% +/- 1.5 (mean +/- SEM) tumor cell kill. When platelets were added to monocytes in a 1:1 ratio, an increase in cytotoxicity to 61% +/- 3.2 was observed. The cytotoxicity noted when platelets were added to a fixed number of monocytes and tumor cells was dependent on the number of platelets added. A decrease in cytotoxicity from 32% +/- 1.5 to 12% +/- 2.3 was observed when contaminating platelets were removed from monocyte preparations. Platelets added to tumor cells in the absence of any monocytes were also toxic, resulting in a maximum kill of 95% at a 4:1 platelet/tumor cell ratio. Secreted products of freshly isolated platelets may be responsible for much of the observed cytotoxicity, since supernatants from the platelets were toxic for tumor cells. Platelets pretreated with a cyclooxygenase inhibitor (ASA) or a lipoxygenase inhibitor had decreased cytotoxicity compared with untreated platelets. Our results indicate that products of platelet arachidonate metabolism are toxic for tumor cell lines. They also suggest that the role of the platelet must be considered when studying monocyte-tumor cell cytotoxicity.     

Elevated NAD(P) glycohydrolase activity: a possible enzymatic marker for malignancy in Burkitt's lymphoma cells

A comparative analysis of enzymatic activities has been performed on 47 human continuous lymphoid lines: 22 tumors derived from Burkitt's lymphoma lines, 6 other lymphomatous long-term cultures, and 19 nonmalignant ties determined on the cell extracts. 4 showed no significant differences between the various lines. They included adenosine diphosphoribose incorporation, glucose-6-phosphate dehydrogenase, cyclic-AMP phosphodiesterase, and glutathione reductase. However, striking differences of activity were found for the enzyme, NAD(P) glycohydrolase (EC 3.2.2.6). Activity levels were, as a mean, four times higher in Burkitt's lymphoma-derived cell lines than in nonmalignant control lines, and the difference was highly significant (p less than 0.02). All Burkitt cell lines containing translocations of chromosome 8 with either chromosomes 2, 14 or 22 showed an increased activity. The specificity and significance of this possible enzymatic marker of Burkitt's lymphoma cells is discussed.     

Bone marrow transplantation for patients with Philadelphia chromosome- positive acute lymphoblastic leukemia

We report the treatment outcome of allogeneic bone marrow transplantation in ten patients with Philadelphia chromosome-positive acute lymphoblastic leukemia. Six patients are alive and well for 6 to 30 months (median 19 months) after transplantation. Four patients died with transplant related complications. In view of the poor prognosis associated with this disease, marrow ablation followed by allogeneic or syngeneic marrow grafting may be the preferred treatment modality if a suitable marrow donor is available.     

Dietary Fat Acutely Increases Glucose Concentrations and Insulin Requirements in Patients With Type 1 Diabetes: Implications for carbohydrate-based bolus dose calculation and intensive diabetes management

OBJECTIVE

Current guidelines for intensive treatment of type 1 diabetes base the mealtime insulin bolus calculation exclusively on carbohydrate counting. There is strong evidence that free fatty acids impair insulin sensitivity. We hypothesized that patients with type 1 diabetes would require more insulin coverage for higher-fat meals than lower-fat meals with identical carbohydrate content.

RESEARCH DESIGN AND METHODS

We used a crossover design comparing two 18-h periods of closed-loop glucose control after high-fat (HF) dinner compared with low-fat (LF) dinner. Each dinner had identical carbohydrate and protein content, but different fat content (60 vs. 10 g).

RESULTS

Seven patients with type 1 diabetes (age, 55 ± 12 years; A1C 7.2 ± 0.8%) successfully completed the protocol. HF dinner required more insulin than LF dinner (12.6 ± 1.9 units vs. 9.0 ± 1.3 units; P = 0.01) and, despite the additional insulin, caused more hyperglycemia (area under the curve >120 mg/dL = 16,967 ± 2,778 vs. 8,350 ± 1,907 mg/dL⋅min; P < 0001). Carbohydrate-to-insulin ratio for HF dinner was significantly lower (9 ± 2 vs. 13 ± 3 g/unit; P = 0.01). There were marked interindividual differences in the effect of dietary fat on insulin requirements (percent increase significantly correlated with daily insulin requirement; R² = 0.64; P = 0.03).

CONCLUSIONS

This evidence that dietary fat increases glucose levels and insulin requirements highlights the limitations of the current carbohydrate-based approach to bolus dose calculation. These findings point to the need for alternative insulin dosing algorithms for higher-fat meals and suggest that dietary fat intake is an important nutritional consideration for glycemic control in individuals with type 1 diabetes.Current guidelines for the intensive treatment of type 1 diabetes focus exclusively on carbohydrate counting for mealtime bolus calculation (1,2). This carbohydrate-based approach to insulin dose calculation assumes that carbohydrate is the only dietary macronutrient that affects glucose levels and insulin requirements.Dietary fat and free fatty acids (FFAs) are known to impair insulin sensitivity and to enhance hepatic glucose production (3,4). Furthermore, pharmacologic interventions that lower FFA levels in nondiabetic and type 2 diabetic individuals lead to both improved insulin sensitivity and glucose tolerance (5,6). Studies in patients with type 1 and type 2 diabetes have shown that dietary fat delays gastric emptying, leading to a lag in glucose absorption (7,8). Although there has been considerable interest in the role of dietary fat and circulating FFAs in the pathogenesis of type 2 diabetes (9,10), relatively little attention has been given to the possible implications of FFA-induced insulin resistance for the treatment of type 1 diabetes. Review of continuous glucose monitoring and food log data from our adult patients with type 1 diabetes led to the observation that, contrary to the current treatment recommendations, higher-fat meals usually require more insulin coverage than lower-fat meals with similar carbohydrate content.Pizza is widely recognized to cause marked late postprandial hyperglycemia in patients with type 1 diabetes (11). Some studies have shown that use of an extended bolus with (12) or without (13–15) an increase in total dose is needed to attenuate hyperglycemia after higher-fat pizza meals. To our knowledge, a controlled study to determine whether changes in dietary fat intake, independent of other macronutrients, leads to alterations in glucose control and insulin requirements in type 1 diabetes has not been undertaken. In this study, we carefully regulated the macronutrient intake of patients with type 1 diabetes undergoing closed-loop glucose control to test the hypothesis that high-fat (HF) meals require more insulin coverage than low-fat (LF) meals with identical carbohydrate content.     

Pheochromocytoma and paraganglioma: comparison of MR imaging with CT and I-131 MIBG scintigraphy

To ascertain the magnetic resonance (MR) imaging characteristics of pheochromocytomas and paragangliomas and to compare MR with computed tomography (CT) and iodine-131 metaiodobenzylguanidine (I-131 MIBG), 19 patients (18 with pheochromocytomas, one with a paraganglioma) were studied. The 18 patients with pheochromocytomas had had positive findings with I-131 MIBG scintigraphy. Abdominal pheochromocytomas were generally hypointense compared with normal liver on T1-weighted MR images and extremely hyperintense on T2-weighted MR images. MR imaging was preferable to CT in the evaluation of primary pheochromocytomas due to superior tissue characterization, particularly in the patient with hypertension and borderline catecholamine levels. For patients with recurrent or metastatic disease, the data suggest that I-131 MIBG scintigraphy is the examination of choice.     

Elevated expression and altered pattern of activity of DNA methyltransferase in liver tumors of rats fed methyl-deficient diets

DNA methyltransferase (MTase) activity in nuclear extracts from neoplastic and preneoplastic livers of rats fed a methyl-deficient diet (MDD) is elevated compared with that seen in the livers of control rats. Nuclear proteins were prepared in the presence of protease inhibitors including trans-epoxy succinyl-L-leucylamido-(4- guanido)butane and were fractionated by isoelectric focusing. In normal, control liver, two distinct MTase fractions were observed. In MDD-induced malignant liver, a third fraction, in addition to the previous two, was also seen. Both the DNA substrate and the cytosine site specificities of the third MTase fraction differ from those of the other two fractions. The distinct MTase activity in liver tumor has significantly more de novo MTase activity than do the MTase fractions of normal, control liver. Thus, normal and neoplastic rat livers differ in DNA MTase fractionation patterns and site specificities. The altered DNA MTase activity observed in rat liver tumors caused by MDDs may be one of the critical factors contributing to cancer formation through abnormal DNA methylation.