v-Crk modulation of growth factor-induced PC12 cell differentiation involves the Src homology 2 domain of v-Crk and sustained activation of the Ras/mitogen-activated protein kinase pathway

Nerve growth factor (NGF) and epidermal growth factor (EGF) elicit contrasting actions on PC12 pheochromocytoma cells; NGF causes neuronal differentiation, and EGF induces proliferation. However, ectopic expression of the Src homology 2 (SH2) and SH3-containing oncogenic adaptor protein v-Crk in PC12 cells results in EGF-inducible neuronal differentiation (Hempstead, B. L., Birge, R. B., Fajardo, J. E., Glassman, R., Mahadeo, D., Kraemer, R., and Hanafusa, H. (1994) Mol. Cell. Biol. 14, 1964-1971). Here we show that v-Crk complexes with both the tyrosine-phosphorylated EGF receptor and the Ras guanine nucleotide exchange factor SOS in PC12 cells and is involved in an pathway analogous to that of Grb2. Expression of v-Crk results in an enhanced and sustained activation of Ras and mitogen-activated protein (MAP) kinase following EGF or NGF stimulation, implying that v-Crk can couple divergent tyrosine kinase pathways to Ras. To investigate the causal relationship between EGF receptor binding, MAP kinase activation, and neurite outgrowth, we stably expressed two v-Crk SH2 point mutants, v-Crk(R273N) and v-Crk(H294R) in PC12 cells. Mutations within the SH2 domain of v-Crk block binding of v-Crk to the tyrosine phosphorylated EGF receptor, compromise v-Crk's ability to cause EGF-dependent neurite outgrowth, and act in a dominant negative manner for NGF-induced neurite outgrowth. However, the kinetics of MAP kinase activation in EGF- or NGF-treated v-Crk-(R273N)PC12 cells was comparable with that in v-CrkPC12 cells. These data are consistent with a model in which v-Crk regulates the strength of a tyrosine kinase signal leading to prolonged activation of Ras and MAP kinase. However, the experiments with the SH2 mutants suggest that sustained activation, by itself, may not be sufficient to switch the fate of v-CrkPC12 cells from proliferation toward differentiation.

The effect of lipoproteins on human glioblastoma growth in vitro

Experiments were performed using an established human glioblastoma cell line to determine the effect of lipoproteins on regulating their growth. It was found that synthetic and natural human high density lipoproteins (HDL) were effective in inhibiting tumor cell growth in a nontoxic, dose-dependent manner, and that the LD50 was 10-fold lower than that for normal rat astrocytes grown under identical conditions. In the presence of the antioxidant, glutathione, essentially all of the growth-inhibiting properties of HDL could be reversed suggesting that oxidized lipids from the HDL interacting with the plasma membranes of the glioblastoma cells were responsible for the growth-inhibiting effect observed. The markedly lower concentration of HDL required to inhibit glioblastoma cells in culture compared to normal astrocytes suggested that the mechanism of HDL-induced inhibition may be important for tumor growth in vivo. One possible mechanism under investigation is the possibility of HDL modulation of a membrane-associated, tumor-specific phosphatase.

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Cis-platinum treatment of metastatic adrenal carcinoma

Cis-platinum was used in the management of four patients with metastatic carcinoma of the adrenal cortex. In each instance, clinical and objective response was observed. This agent would appear to warrant further trial in the management of this rare tumour.

Pseudodelirium

Two case histories are presented which illustrate the fact that acute functional psychoses may simulate delirium. It is suggested that the term "pseudodelirium" may alert clinicians to this possibility, and facilitate the earlier diagnosis and treatment of psychiatric illness.

Null cell chronic lymphocytic leukaemia

Lymphocytes lacking receptors for sheep erythrocytes and surface immunoglobulin were present in the blood in large numbers at some stage in four cases of chronic lymphocytic leukaemia (which included a mother and son), and formed a substantial proportion of the circulating lymphocytes in other cases. These null cells possessed receptors for mouse erythrocytes. Other B-cell markers were also found on these cells. Serial studies showed a great variation in the number of null cells during the course of the disease (which may be associated with treatment), suggesting variation in the the maturation of leukaemic cells, and indicating that the surface marker complement may not reflect the constitution of the cell undergoing the original malignant change.

A retrospective analysis of the TATs of children at risk who subsequently broke down

A retrospective evaluation of stories told to three Thematic Apperception Test (TAT) cards by children at risk isolated six characteristics that were associated with functioning six to 10 years later. The characteristics included lack of individual initiative, denial of mother-child relationships, denial of negative outcomes, and lack of autonomy. The TATs of children at risk (due to one parent's hospitalization for a psychotic illness) who subsequently suffered major decompensation themselves (requiring hospitalization or intensive outpatient therapy) could be discriminated from those of children at risk with apparently normal development. The TAT characteristics were independent of the level of adjustment at the time the TATs were administered, not related to the child's IQ, socioeconomic status, race, or other family characteristics, and moderately negatively correlated with story length.

Platelet metal levels in normal subjects determined by atomic absorption spectrophotometry

A method has been developed for the estimation of iron, copper, zinc, calcium and magnesium in human platelets using atomic absorption spectrophotometry. Fe and Cu are either absent or present in very low concentration approaching the limit of detection: Zn, Ca and Mg are readily detectable. EDTA is preferable to ACD(A) or heparin as the anticoagulant for collection in that the platelet yield is reliable: however, slightly low results for Ca and Mg are obtained. Corrections for residual plasma and contaminating red cells are essential. Plasma and platelet metal levels in 33 normal subjects are reported together with the findings in four studies undertaken on platelets obtained from subjects with polycythemia vera.

Technetium-99m-pyridoxylideneglutamate: a new hepatobiliary radiopharmaceutical. II. Clinical aspects

Technetium-99m-pyridoxylideneglutamate (99mTc-PG) is a nontoxic radiopharmaceutical that was found to undergo rapid biliary excretion in normal humans. The biliary tree and gallbladder were seen within 10-15 min of injection and by 20 min marked accumulation of radioactivity was noted in the gallbladder and gastrointestinal tract. Of ten "control" volunteers, seven had normal 99mTc-PG-cholescintigrams. In the remaining three, the gallbladder was not visualized. Gallbladder disease was not excluded in these three subjects. Of 24 patients referred for investigation of right upper quadrant abdominal pain, 13 proved to have gallbladder disease. All seven patients with acute cholecystitis and one of four patients with chronic cholecystitis had nonvisualization of the gallbladder on the cholescintigram whereas five patients with chronic cholecystitis or cholesterolosis had normal cholescintigrams. Six of the eight patients with nonvisualization of the gallbladder on cholescintigram had contrast radiologic studies (oral cholecystogram or intravenous cholangiogram or both), and in all six, nonvisualization of the gallbladder was also reported on the contrast study. cholescintigraphy was found to be greatly inferior to contrast radiologic studies in the detection of gallbladder stones. Eleven patients had complete extrahepatic biliary obstruction and this diagnosis was correctly made in all 11 by the cholescintigram. Fourteen patients had incomplete extrahepatic biliary obstruction. The correct diagnosis was made on the cholescintigram in seven but in the remaining seven it was not possible to distinguish between incomplete extrahepatic biliary obstruction and hepatocellular disease. Malignant lesions (carcinomas of head of pancreas, gallbladder, common bile duct or ampulla of Vater) were the cause of obstruction in 10 of the 25 patients with complete or incomplete obstruction and the diagnosis of obstruction due to malignancy was correctly made in 8 of these 10 by means of a scintigraphic equivalent to Courvoisier's sing. Finally, 11 patients had hepatocellular disease and a nonspecific pattern consistent with either imcomplete biliary obstruction or hepatocellular disease was observed on the cholescintigram in all 11. The 99mTc-PG cholescintigram is suggested for a role complementary to that of contrast radiologic studies in the preoperative investigation of patients with possible surgical disease of the biliary tract. Contrast radiologic techniques are advocated as being more appropriate in the nonjaundiced patient with suspected gallbladder disease whereas the 99mTc-PG cholescintigram is advocated as being more appropriate in the patient with jaundice. The value of the 99mTc-PG cholescintigram lies in the confidence with which complete extrahepatic biliary obstruction can be diagnosed. The "scintigraphic Courvoisier's sign" seems a useful indicator of malignant obstruction.

Platelet ascorbic acid levels in normal subjects and in disease

The platelet ascorbic acid concentration was measured in 26 normal subjects and found to be 20 times as high as in plasma. This is in agreement with previous reports in the literature. The platelets of patients with uraemia, leukaemia, and megaloblastic anaemia had a lower than normal platelet ascorbic acid content. In uraemia and megaloblastic anaemia the plasma ascorbic acid concentration was normal suggesting that a platelet defect may be responsible for the low platelet ascorbic acid content. In leukaemia the low platelet ascorbic acid content is probably secondary to a low plasma level.

The diagnosis of pulmonary embolism: a review with particular reference to the use of radionuclides

Pulmonary embolism was first recognized as an important entity early in the nineteenth century. The evolution of our knowledge of this disorder has been reviewed with particular emphasis on the various diagnostic techniques which have been used to assist in its recognition. These have included physical examination to demonstrate the presence of classical physical signs, electrocardiography, biochemical tests, radiological examinations, pulmonary function tests, ultra-sound and methods employing radionuclides. The wide variety of techniques applied to this problem clearly indicates that no currently available test is entirely satisfactory alone. Probably the most significant advance in recent years has been the development of lung perfusion scanning which has provided at the very least a valuable screening test and a ready method of studying serially the natural history of the perfusion defects produced by thromboembolic disease.

New method for the estimation of platelet ascorbic acid

Present techniques for the estimation of platelet ascorbic acid allow interference by other substances in the sample. A new and more specific method of analysis is presented. The proposed method owes its increased specificity to resolution of the extract by thin-layer chromatography. By this means ascorbic acid is separated from other reducing substances present. The separated ascorbic acid is eluted from the thin layer and estimated by a new and very sensitive procedure: ascorbic acid is made to react with ferric chloride and the ferrous ions so formed are estimated spectrophotometrically by the coloured derivative which they form with tripyridyl-Striazine. Results obtained with normal blood platelets were consistently lower than simultaneous determinations by the dinitrophenylhydrazine (DNPH) method.