Angiographic and scintigraphic findings in fibrosing mediastinitis

The clinical and morphologic findings in the case of a 47-year-old man with fibrosing mediastinitis, most probably due to histoplasmosis, are described. Radionuclide angiography demonstrated obstruction of the superior vena cava with collateral vascularization. Computed tomography demonstrated a large calcific mass interposed between the pulmonary artery and superior vena cava suggesting potential pulmonary vasculature involvement. For this reason, pulmonary scintigraphy was performed which showed right lung perfusion and ventilation defects. Radionuclide angiography and pulmonary scintigraphy complement each other in determining the extent of vascular involvement with fibrosing mediastinitis. However, contrast venography is necessary to correctly delineate the anatomy of the obstructed superior vena cava and its collaterals.

Predicting the cure of osteomyelitis under treatment: concise communication

The right tibias of sixty-six rabbits were injected with a suspension of Staphylococcus aureus and sodium morrhuate. After four weeks, 43 rabbits developed osteomyelitis and were started on a course of antibiotics. During treatment a gallium-67 scintigram was obtained every two weeks, for up to 10 weeks. During the treatment weeks, 25 rabbits developed negative gallium-67 scintigrams and were killed. All 25 had negative bacteriologic cultures of the right tibia. At the end of 10 wk after start of treatment, the 18 rabbits with persistently positive scintigrams were killed. Eleven of these had positive bacteriologic cultures of the tibia, and seven were negative. The findings suggest that sequential gallium-67 scintigrams may be useful in predicting the cure of osteomyelitis during treatment.

Effect of GnRH antagonist, [Ac-delta 3Pro1, pFDPhe2, DTrp3,6] GnRH, on pulsatile gonadotrop in secretion in the castrate male primate

Three different doses of a potent antagonist to GnRH, [Ac-delta 3Pro1, pFDPhe2, DTrp3,6], GnRH were compared in adult male monkeys to determine the acute effect on pulsatile gonadotropin secretion. In accomplishing these studies, blood was drawn at 15 min intervals over 24-30 h without anesthesia using a mobile vest and tether assembly to support an indwelling cannula. After a 3 to 6 h control period, 2.0, 0.2 or 0.02 mg GnRH antagonist/kg bw in 1 ml corn oil sc, was given to castrate adult monkeys. The highest dose decreased circulating LH (by radioimmunoassay and bioassay) and FSH whereas the intermediate dose decreased LH only. The higher dose produced both a more prolonged and greater reduction in circulating gonadotropins. These data demonstrate that this GnRH antagonist can reduce serum gonadotropins both acutely and for intervals greater than 24 h.

Properties and regulation of the T lymphocyte insulin receptor

Primary human T lymphocytes that have been mitogen activated in chemically defined medium express cell surface insulin receptors. The receptor is identical to other mammalian insulin receptors in binding properties, including: pH dependency, ligand affinity, hormone specificity, and cooperative interactions. Scatchard plots are curvilinear and a ligand-induced increase in dissociation, the property normally associated with "negative cooperativity", is kinetically demonstrable. In vitro insulin treatment of the receptor-negative, resting T lymphocyte slightly enhances the degree of insulin binding which emerges following cellular activation. Insulin treatment of receptor-positive lymphoblasts results in insulin receptor "down-regulation". These findings indicate that T lymphoblast insulin receptor concentrations are not significantly influenced by insulin before their emergence but are dramatically regulated by insulin following their appearance at the cell surface.

Failure of protein synthesis inhibition to block progesterone desensitization of lordosis in female rats

Progesterone's desensitization effect on lordosis has been shown to correlate with a decreased concentration of hypothalamic progestin receptors after progesterone injection. In a recent study, one group of investigators found that the protein synthesis inhibitor anisomycin appeared to block progesterone's desensitization effect. Despite decreased levels of cytoplasmic progestin receptors, progesterone + anisomycin-treated rats exhibited a high level of lordosis four hr after a second progesterone injection. Because this finding conflicts with a progestin receptor model of progesterone's desensitization effect, we investigated it further. In the first experiments, ovariectomized rats were injected with estradiol benzoate followed 24 hr later by either progesterone or vehicle. Anisomycin injected 3 hr after progesterone, at a dose that causes inhibition of hypothalamic protein synthesis for at least 4 hr, was without effect on progesterone desensitization a day later. In other experiments silastic implants containing estradiol were inserted into ovariectomized rats. Forty-five hr later, rats received progesterone or vehicle, followed by injections of anisomycin or saline. Rats receiving anisomycin + progesterone were still highly receptive at 30 hr while saline + progesterone controls were not. Furthermore, the results were similar 4 hr after a second injection of progesterone at 30 hr. In a related experiment, we confirmed that anisomycin delayed dramatically termination of the period of sexual receptivity. In this laboratory anisomycin does not seem to block progesterone's desensitization effect. However, with certain procedures anisomycin delays the termination of sexual receptivity. Thus it is important in investigations of the mechanism of progesterone's desensitization effect that animals be tested prior to the second progesterone injection to determine if they are actually responding to the progesterone.

Amoebae from antarctic soil and water

Samples of soil and water were taken from the McMurdo Sound-Dry Valley region of Antarctica. Of the 70 samples cultured, 22 yielded amoebae capable of clonal growth at 30 degrees C. None of the isolates was pathogenic for mice. Acanthamoeba isolates appeared to show better survival potential than Naegleria isolates.

Phenobarbital overdose: a kinetic approach

A case that utilizes a pharmacokinetic approach to evaluate the need for withdrawal prophylaxis after a phenobarbital overdose is presented. To date, the practitioner has had to rely on an accurate drug-use history to predict which patients may be at risk for withdrawal symptoms. Since this information is often difficult to obtain, some other means of identifying potential withdrawal-syndrome patients would be useful. This case describes the successful use of kinetically determined parameters, the elimination rate constant and half-life, in predicting withdrawal potential. This easily used kinetic approach may provide practitioners with a useful tool for predicting those patients at risk for withdrawal symptoms following phenobarbital overdose.

Regulation of insulin receptors in erythroid cells

Previous studies using inhibitors have suggested that protein synthesis is necessary for "down-regulation" of insulin receptors. We have tested this hypothesis without the use of inhibitors by studying the ability of cells of the erythroid series to down-regulate their insulin receptors in vitro. The cells tested include mature erythrocytes and reticulocytes from rabbits and Friend erythroleukemia cells (a model for the basophilic erythroblast, a primitive nucleated erythrocyte). All cells were maintained at 37 degrees C for 18 hr +/- insulin (10(-8)M). Cultures were then incubated with phosphate buffered salines (pH 7.0) at 30 degrees C for 40 min to remove bound insulin. Receptors were quantitated by computerized analysis of Scatchard plots of subsequent insulin binding studies. Cells fully capable of both mRNA synthesis and protein synthesis, such as the undifferentiated and differentiated Friend erythroleukemia cell, had reduction of insulin receptors at 60% and 43%, respectively. Reticulocytes, which were capable of protein synthesis but not mRNA synthesis, had decreases of 25%-30% in 8 separate experiments. Mature erythrocytes, capable of neither RNA nor protein synthesis had no significant changes in receptor concentrations. Since mature erythrocytes do not "down-regulate" their insulin receptor concentration, studies of these receptors in erythrocytes of patients should be interpreted with caution.

Scintigraphic findings in progressive diaphyseal dysplasia

A 14-yr-old white male with a severe form of progressive diaphyseal dysplasia (Engelmann-Camurati disease) was referred to our institution for evaluation of splenomegaly, which is not usually associated with the disease. Our studies included bone-marrow, and liver-spleen scans. These scintigraphic findings, along with the probable cause for splenomegaly, are discussed.

Stimulation by polypeptides of dehydroepiandrosterone sulphate synthesis in human fetal adrenal slices

Slices of human fetal adrenal glands (obtained after abortion at 10-18 weeks of gestation) were superfused sequentially with buffer or with buffer incorporating human ACTH, synthetic ACTH (1-24), human GH, human chorionic gonadotrophin, alpha-melanocyte stimulating hormone, metenkephalin, ovine prolactin, beta-lipotrophic hormone or corticotrophin-like intermediate lobe peptide in concentrations from 10(-6) to 10(-9) mol/l. Changes in the concentration of dehydroepiandrosterone sulphate (DHAS) in the effluent in response to addition or removal of the polypeptides were measured by radioimmunoassay. Comparison of the quantity of DHAS in the effluent collected during superfusion (5h) with that present in the tissue initially indicated that synthesis of this conjugated steroid occurred during superfusion. Increases in the concentration of DHAS in the effluent were provoked by exposure of the tissue to all the polypeptides except corticotrophin-like intermediate lobe peptide. These effects were unlikely to be non-specific since incorporation of gonadotrophins, albumin or dextran into the superfusate did not stimulate corticosteroid synthesis from viable bovine adrenal tissue. It was concluded that a number of pituitary polypeptides have the potential to provoke androgen sulphate synthesis by the human fetal gland in early gestation. Consequently there may be no single fetal corticotrophin at this stage and androgen production may be regulated by a number of trophic factors.

Effect of the membrane lipid environment on the properties of insulin receptors

We have altered the fatty acid composition of the Friend erythroleukemia cells and studied the effect on the binding parameters of the insulin receptor. Cells were grown for about five generations in media enriched with oleate (a monounsaturated fatty acid) or linoleate (a polyunsaturated fatty acid). The microsomal phospholipids normally contained about 40% saturated, 40% monounsaturated, and 20% polyunsaturated fatty acids. In cells grown with oleate, monounsaturates rose to 63% and in cells grown with linoleate, the polyunsaturated component rose to 52%. Fluidity determination by electron spin resonance similarly indicated that the membranes of cells grown in linoleic acid were more fluid than those grown in oleic. Control cells demonstrated the least membrane fluidity.

The cells enriched in unsaturated fatty acids had an increased number of insulin receptors and decreased receptor affinity, but the exact interpretation of the change was dependent on the method of data analysis. When analyzed assuming negative cooperativity among a single class of receptors, there was an increase in receptor number from 23,000/cell in the control cells to 39,000/cell in the oleate-enriched and to 81,000/cell in the linoleate-enriched cells. These changes were accompanied by reciprocal decreases in the affinity of both the unoccupied form of the receptor (Ke) and the occupied form of the receptor (Kf). When analyzed assuming two independent classes of sites, there was no major change in the number or affinity of the high affinity receptors (6000–8000/cell). There was, however, a marked increase in the number of low affinity receptors from 15,000/cell in the control cells to 32,000/cell in the oleate-enriched and 74,000/cell in the linoleate-enriched cells. This increase in receptor concentration was again accompanied by a reciprocal decrease in the affinity of the low affinity receptor.

These studies thus demonstrate a relationship between the cellular fatty acid composition and the properties of insulin receptors. The observed changes could be due to alterations in the quaternary structure Of the receptor.

Immunity to pathogenic free-living amoebae: role of humoral antibody

Pathogenic free-living amoebae are common in nature, but few clinical infections by these amoebae have been reported. This has prompted studies of host susceptibility factors in humans. A survey of normal human sera from three New Zealand Health Districts was made; antibodies to pathogenic free-living amoebae were found in all sera, with titers ranging from 1:5 to 1:20 for Naegleria spp. and from 1:20 to 1:80 for Acanthamoeba spp. The antibodies belonged mainly to immunoglobulin G and immunoglobulin M classes. The presence of a specific neutralizing factor against Acanthamoeba spp. but not Naegleria spp. was demonstrated. Possible protective mechanisms are discussed.

Immunity to pathogenic free-living amoebae: role of cell-mediated immunity

The role of cell-mediated immunity in defense against pathogenic free-living amoebae was examined. Both the in vitro macrophage inhibition test and the in vivo delayed hypersensitivity test showed responses to both heterologous and homologous antigens, although homologous systems were the most efficient. It is suggested that exposure to nonpathogenic species of free-living amoebae can stimulate the immune system to be effective against pathogenic species. The significance of cell-mediated immunity as a defense against invasion by pathogenic free-living amoebae is discussed.

Effect of disinfectants on pathogenic free-living amoebae: in axenic conditions

The amoebicidal properties of chlorine, chlorine dioxide, ozone, and deciquam 222 were examined in axenic conditions. Naegleria spp. were found to be more sensitive to chlorine and chlorine dioxide than Acanthamoeba spp. No marked difference in sensitivity to ozone or deciquam 222 could be detected between the pathogenic (A-1) and nonpathogenic (1501) strains of Acanthamoeba and the pathogenic (MsT) and nonpathogenic (P1200f) strains of Naegleria. Methods of disinfection are discussed with reference to suitability of the disinfectants to real conditions.

Primary amoebic meningo-encephalitis in an indoor heat-exchange swimming pool

The case history, identification and isolation of the aetiological agent of a case of primary amoebic meningo-encephalitis (PAM) contracted in an indoor heat-exchange pool are presented. The isolated strain (MsM) is compared with known strains of pathogenic and non-pathogenic Naegleria.

Triiodothyronine metabolism in diabetic rats

Triiodothyronine (T3) metabolism was assessed in untreated and in insulin-treated diabetic rats and the results compared with a corresponding control group. Male rats of the Wistar strain were made diabetic by the intraperitoneal injection of alloxan in a dose of 17.5 mg/100 g body weight and thereafter maintained normoglycaemic for a week and until 24 h before initiation of the study. The average glycaemia in control and in insulin-treated animals was 135 mg/100 ml, whereas in the untreated diabetic rats it was 455 mg/100 ml. Each animal was injected a tracer dose of [125I]T3 containing 2 μCi of 125I and 15 ng of T3. Heparinized blood samples were obtained by cardiac puncture at 5, 18 and 24 h following the injection of the tracer. The excretion of inorganic 125I in the 24-h collections of urine was also determined. The kinetics of [125I]T3 were studied by the extrapolation method using the straight line of plasma disappearance between 5 and 24 h. It was found that the untreated diabetic rats had a significant slowing of plasma disappearance of labelled T3. The decrease in fractional hormone turnover was balanced by a slight expansion of the distribution space, which presumably led to a larger hormone pool and a normal degradation rate of T3. These events seemed substantiated by the normal excretion of 125I in the urine observed in untreated animals. A parallel study of plasma hormone binding using a red cell uptake method showed a significant reduction of binding avidity for T3 by plasma proteins in the untreated diabetic animals. The administration of insulin restored plasma T3 kinetics and binding avidity to normal, as observed in control rats. It was concluded that untreated diabetes mellitus induced changes in T3 kinetics and in T3 serum binding without altering hormone deiodination, parameter which reflects tissue utilization of T3.