Thirty years on: examination performance and career success of the 1950-1 intake of Cambridge medical students

The relation between preclinical tripos and clinical examination results and subsequent career success of 188 medical graduates of Cambridge University was measured using five indicators of success. A generally positive relation was found, but this was not specific enough to make accurate individual predictions. Present levels of appointment were more closely related to clinical than preclinical results. No support was found for the local assertion that "2.1s" do better than "firsts" in clinical medicine. Since undergraduate examination results seem to be inaccurate predictors of later performance they should not be used as the principal evidence in making selection decisions.

Influence of the state of ribosome association on the phosphorylation of ribosomal proteins in isolated ribosome--protein kinase systems from rat cerebral cortex

Ribosomal protein phosphorylation was investigated in isolated ribosomal subunits and polyribosomes from rat cerebral cortex in the presence of [gamma-32P]ATP and purified catalytic subunit of cyclic AMP-dependent protein kinase from the same tissue. Ribosomal proteins that were most readily phosphorylated in isolated cerebral ribosomal subunits included proteins S2, S3a, S6 and S10 of the 40 S subunit and proteins L6, L13, L14, L19 and L29 of the 60 S subunit. These proteins were also phosphorylated in cellular preparations of rat cerebral cortex in situ or in vitro [Roberts & Ashby (1978) J. Biol. Chem. 253, 288-296; Roberts & Morelos (1979) Biochem. J. 184, 233-244]. However, several additional ribosomal proteins were phosphorylated when isolated 40 S or 60 S subunits were separately incubated in the reconstituted system. Analogous results were obtained with an equimolar mixture of cerebral 40 S and 60 S subunits under comparable conditions. In contrast, extensive exposure of purified cerebral polyribosomes to the catalytic subunit resulted in phosphorylation of only those ribosomal proteins of the 40 S subunit that were most highly labelled after the administration of [32P]Pi in vivo: proteins S2, S6 and S10. Ribosomal proteins of 60 S subunits that were readily phosphorylated in isolated cerebral polyribosomes included proteins L6, L13 and L29. These results indicate that polyribosome formation markedly decreases the number of ribosomal protein sites available for phosphorylation by the catalytic subunit of cyclic AMP-dependent protein kinase. Moreover, the findings suggest that, of the ribosomal protein phosphorylations observed in rat cerebral cortex in vivo, proteins S2, S6, S10, L6, L13 and L29 can be phosphorylated in polyribosomes, whereas proteins S3a, S5, L14 and L19 may become phosphorylated only in free ribosomal subunits.

Value of small bowel enema in incomplete intestinal obstruction

The usefulness of small bowel enema X-ray examination was evaluated in 11 patients in whom a provisional diagnosis of incomplete small bowel obstruction was made. Dilute barium was introduced through a nasojejunal tube. In one patient intubation of the jejunum was unsuccessful. In six patients the suspected obstruction was confirmed and information obtained about the site of obstruction. The small bowel enema X-ray examination was normal in three patients and subsequent clinical outcome was uneventful. In one patient, with normal findings on small bowel enema X-ray examination, acute obstruction developed after two days, necessitating operation. Small bowel enema X-ray examination appears a worthwhile adjuvant to clinical assessment but decisions for operative intervention still need to be based on clinical evaluation of patients.

Characterization of infant rat cerebral cortical membrane proteins phosphorylated in vivo: identification of the ACTH-sensitive phosphoprotein B-50

This study on the phosphorylation in vivo of membrane proteins in cerebral cortices of infant rats reports the identification of the adrenocorticotropin (ACTH)-sensitive phosphoprotein B-50 as one of the substrate proteins that are rapidly phosphorylated in vivo following intracisternal administration of 2 mCi [32P]orthophosphate. Rats were sacrificed 30 min after isotope injection. A fraction enriched in membranes, designated neural membranes (NM), was isolated from the cerebral cortices according to the procedure used for preparation of synaptic plasma membranes (SPM) from adult brain. This NM fraction was characterized by electron microscopy. The proteins of NM were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Numerous protein bands of NM in infant rat brain were phosphorylated in vivo. Attention was focussed on the 32P-labeled protein bands in the molecular weight range of 47K-67K. In this region one phosphoprotein band (MW 48K) was more highly labeled than the other bands. The electrophoretic behavior of three of these labeled bands, designated a, c, and e (MW 48K, 55K, and 62K, respectively) was compared with that of protein bands that were phosphorylated in vitro in cerebral membranes isolated from noninjected infant rats. The effects of ACTH1-24 and cyclic AMP in the in vitro system were also studied to probe for the presence of specific membrane proteins known to be sensitive to these modulators. On incubation of NM with [gamma-32P)ATP in the presence and absence of ACTH1-24 in vitro, phosphorylation of a 48K protein band was inhibited in a dose-dependent fashion by the neuropeptide. Two-dimensional electrophoretic separation of NM proteins labeled in vivo indicated that the 48K band had an isoelectric point of 4.5, identical to that of the ACTH-sensitive B-50 protein previously identified. Cyclic AMP stimulated phosphorylation in vitro of two protein bands (MW 55K and 59K) in NM preparations. This result indicates that the in vivo labeled band c may correspond to the cyclic AMP-sensitive 55K protein, whereas phosphoprotein band e, labeled in vivo, appears to be different from the cyclic AMP-sensitive 59K protein band. These observations indicate that neural membranes isolated from infant rat cerebral cortices contain a variety of proteins that can be phosphorylated in vivo. Several of these, for example, the 48K protein band, have the properties of synaptic plasma membrane proteins of adult rat brain that have been characterized by their sensitivity to neuromodulators in endogenous phosphorylating systems in vitro.

Clinical experience with malignant pheochromocytomas

In a 30 year period at Vanderbilt University Hospital, the affiliated Nashville General Hospital and the Nashville Veterans Administration Hospital, 64 patients with pheochromocytoma have been observed. In eight of these, the tumor proved to be malignant. Retrospective review of biologic characteristics of pheochromocytomas in this series included clinical, diagnostic imaging, chemical and histopathologic data. Aside from presence of distant metastases, none of these features had predictive value in indicating the biologic malignant nature of the primary tumor. One patient has been cured by radical surgical resection for 16 years. Three others have died with metastatic tumor and three patients are alive with metastatic tumor.

Inhibition of cerebral protein kinase activity and cyclic AMP-dependent ribosomal-protein phosphorylation in experimental hyperphenylalaninaemia

Studies were carried out to elucidate the mechanisms underlying the diminished phosphorylation of cerebral ribosomal protein in experimental hyperphenylalaninaemia [Roberts & Morelos (1980) Biochem. J.190, 405-419]. Administration of N(6),O(2)'-dibutyryl cyclic AMP or 3-isobutyl-1-methylxanthine, which increased phosphorylation of the S6 protein of cerebral 40S ribosomal subunits in control infant rats, did not counteract the decreased phosphorylation of this ribosomal protein resulting from intraperitoneal administration of a loading dose of l-phenylalanine. N(2),O(2)'-Dibutyryl cyclic GMP had no effect on cerebral ribosomal-protein phosphorylation in either control or hyperphenylalaninaemic animals. The phenylalanine-induced decrease in ribosomal-protein phosphorylation was associated with decreased protein kinase activity in cerebral cytosolic and microsomal preparations. However, the maximal protein kinase response to cyclic AMP added in vitro was unaltered by prior administration of phenylalanine in vivo. The heat-stable protein inhibitor of cyclic AMP-dependent protein kinases decreased the activity of these enzymes by about 90% and eliminated the phenylalanine-induced difference in protein kinase activity in the absence of added cyclic AMP. Intracisternal administration of doses of dibutyryl cyclic AMP or 3-isobutyl-1-methylxanthine which increased the cyclic AMP-dependent protein kinase activity ratio in control infant rats was without effect on this index in phenylalanine-treated animals. Dibutyryl cyclic GMP had no effect on the protein kinase activity ratio in either group of animals. These results suggest that inhibition of cerebral cyclic AMP-dependent protein kinases by abnormally high concentrations of phenylalanine may contribute to the decrease in cerebral ribosomal-protein phosphorylation in experimental hyperphenylalaninaemia.

Biochemical changes of intervertebral discs in patients with spondylolisthesis or with tears of the posterior annulus fibrosus

Surgically removed discs from patients with either spondylolisthesis or tears of the posterior annulus fibrosus were analysed for water, proteoglycan, and collagen content and compared with post-mortem control material. Discs from patients with spondylolisthesis had a reduced proteoglycan content in all section sampled and less collagen in the outer annular layers. In contrast discs containing tears in the posterior annulus were unaltered biochemically, although extended studies on 2 patients indicated that there may be localised biochemical changes in the region of the tear itself. Collagen types I, II, and III and proteoglycan distributions were studies qualitatively by immunofluorescence. Collagen types I and III appeared to be reduced in discs from patients with spondylolisthesis, but again little change was found in patients with tears in the posterior annulus fibrosus.

Cross-modal use of an internal clock

Four experiments used time-discrimination procedures with rats to ask if light and sound are timed by the same internal clock and if measured durations of light and sound are stored in the same memory. Experiment 1 used a choice procedure and a cross-modal transfer-of-training design. Rats were trained to press one lever after a 1-sec signal, another lever after a 4-sec signal. At first, the signal was light (or sound); when performance was accurate, the signal was changed ot sound (or light). There was transfer of the time discrimination across modalities: To some extent, the rats treated the new signal (sound) as if it were the old signal (light). The rest of the experiments used the peak procedure, which is similar to a discrete-trials fixed-interval procedure. With the peak procedure, response rate reaches a maximum in the middle of the trial; the time of the maximum (peak time) is a measure of the clock and temporal memory. Experiment 2 found that changing the time of food during light (or sound) changed peak time during sound (or light). In Experiments 3 and 4, intervals of light (or sound) were followed by intervals of sound (or light). The interval of light decreased the peak time measured from the start to the interval of sound, whether the two intervals were adjacent (Experiment 3) or separated by 5 sec (Experiment 3). Experiments 1 and 2 suggest that measured durations of light and sound are stored by the same memory; Experiments 3 and 4 suggest that light and sound are timed by the same clock.

An evaluation of medical students' practical experience upon qualification

The acquisition of many practical skills-including competence to take initial responsibility for managing serious or life-threatening situations-is rarely assessed in formal medical qualifying examinations in the UK. This paper reports an investigation of two groups of graduands' experiences of practical procedures and acute conditions. Similar patterns of experience were reported by students undertaking their clinical work in different medical schools, including the lack of opportunity to practise certain procedures. A large proportion felt incompetent to manage emergencies. The study demonstrates how a simple self-reporting technique can provide useful data and identify problems of continuity between two stages of medical education-the undergraduate period and the pre-registration year.

Present status and future prospects for the hybridoma technology

A somatic cell genetic technique has recently been developed that makes it possible to obtain very large amounts of homogeneous antibodies and to replenish the supply of the exact same antibodies whenever they are needed. This hybridoma technology has already contributed to major scientific advances and will surely improve the diagnosis and treatment of many diseases. Because the technology itself is relatively simple and inexpensive, it has captured the attention of basic scientists, clinicians, and industrial managers and investors.

Immunofluorescent staining for collagen and proteoglycan in normal and scoliotic intervertebral discs

Specific antisera to collagen Types I, II and III and proteoglycan were used to investigate the distributions of these molecules in normal human intervertebral discs. Immunofluorescent staining indicated the presence of small amounts of Type III collagen located pericellularly in normal adult intervertebral discs. This finding had not been demonstrated previously by other methods. Similar specimens of intervertebral discs from 17 patients with scoliosis of varying aetiologies were examined, but no evidence was obtained for primary connective tissue defects. Secondary changes, especially marked vascularisation of the inner annulus, were apparent in a number of scoliotic discs, and some of these showed enhanced staining for collagen Type I and proteoglycan, and intercellular matrix staining for Type III collagen.

Characterisation of a new tumorous-head mutant of Drosophila melanogaster

A new homoeotic mutant, I127, showing abnormal growths in the head region including homoeotic transformation of eye to genitalia and antenna to leg, was isolated in a screen designed to find new alleles of the tumourous head (tuh-3), mutation. Similarities in the phenotype and genetics of the mutant, and complementation studies with tuh-I; tuh-3, suggest that I127 is indeed an allele of tuh-3. In combination with the first chromosome modifier tuh-1, the mutant is temperature-sensitive during the third larval instar, giving an increased penetrance of the tumorous head phenotype when reared at 25 degrees C as opposed to 18 degrees C. The isolation of further alleles at the tumorous-head locus are essential. The type of morphological defects which can result from mutations at this locus would enable us to establish if this is a complex locus, and if null mutations are lethal during development. The interactions of the tumorous-head gene with first chromosome modifiers and other homoeotic mutations will only be understood if we are able to induce a number of mutations at this locus, and as a consequence begin to elucidate the role of the wild-type gene product in normal development.

Monoclonal antibodies

Serologic reagents have played an important role in the diagnosis, treatment, and epidemiology of infectious diseases. A new technology has been developed for generating homogeneous antibodies that can be produced in large amounts and are available indefinitely. This technique promises to increase the reliability and sensitivity of immunoassays and may even provide antibodies that can be used safely in vivo.

Hybridomas as a source of antibodies

Hybridomas, the progeny of fusion between antibody-secreting spleen cells and myeloma cells, produce large quantities of a single species of antibody. They are an ideal source of serologic reagents since they can be grown in tissue culture, frozen, stored, and recovered when needed. Impending applications include production of monoclonal antibodies to a wide variety of serum components and pathogens.

Methamphetamine and time estimation

Three experiments were conducted to determine the effect of methamphetamine on the performance of rats in two timing tasks. When food sometimes followed the first response after T sec of a signal, the response rate increased to a peak near T sec and then declined. Methamphetamine decreased the time of the peak (Experiments 1 and 2). When one response (called a "short response") was reinforced following a short signal and a different response (a "long response") was reinforced following a long signal (where the short and long signals were 1 and 4, 2 and 8, or 4 and 16 sec), the probability of a long response increased as a function of signal duration. The point of indifference (50% long response) occurred near the geometric mean of the extreme durations, and methamphetamine decreased the point of indifference by about 10%. These results suggest that methamphetamine increases the speed of an internal clock used by rats in time discrimination tasks.

Cause of death in patients with rheumatoid arthritis with particular reference to azathioprine

Three hundred and eleven patients with classical or definite rheumatoid arthritis were observed over an 11-year period. This group is of particular interest since 214 patients were given cytotoxic therapy, 203 were treated with azathioprine (52 of these also received chlorambucil or cyclophosphamide), and 11 were treated with cyclophosphamide or chlorambucil alone. Forty-six patients died. This is an excess mortality compared with the expected rate for the general population matched with respect to age and sex. The death rate was higher than expected in the age group 45-64 years but lower in those aged 75 years or over. There were more deaths from neoplasia and ischaemic heart disease in the younger age group. One patient died of lymphosarcoma; treatment had been with corticosteroids, gold, and chloroquine. No other tumours of the reticuloendothelial system were recorded, and no patient developed leukaemia.

Cerebral ribosomal protein phosphorylation in experimental hyperphenylalaninaemia

Investigations were carried out on the effects of phenylalanine loading on ribosomal protein phosphorylation in cerebral cortices of infant rats. Administration of L-phenylalanine intraperitoneally, in doses of 1 or 2 mg/g body wt., resulted within 30 min in a significant decrease in incorporation of radioactivity from intracisternally administered [32P]Pi into constitutive ribosomal proteins of the cerebral 40S subunit. This phenomenon was not accompanied by significant variations in 32P uptake into the cerebral cytosol. Incorporation of radioactivity into ribosomal proteins of the cerebral 60S subunit exhibited only minor variations under these circumstances. Alterations in the phosphorylation state of cerebral 40S ribosomal proteins induced by phenylalanine loading involved principally the S6 protein, which exists in multiple states of phosphorylation. The proportions of the more highly phosphorylated congeners of this protein were markedly decreased, as detected by two-dimensional electrophoretograms and autoradiographs of the cerebral 40S ribosomal proteins. Phenylalanine loading also altered the relative extent of phosphorylation of the S6 protein in cerebral polyribosomes and monoribosomes. In control animals, the specific radioactivity of 40S proteins in cerebral polyribosomes was five to ten times that of 40S proteins in the monoribosome population. At 1 h after phenylalanine administration, the specific radioactivities of 40S proteins in the two ribosome populations tended to approach equality. These alterations in ribosomal protein phosphorylation were accompanied by a decrease in the proportion of polyribosomes in purified ribosome preparations isolated from cerebral cortices of phenylalanine-treated infant rats. In animals given the higher dose of phenylalanine (2 mg/g body wt.), subsequent administration of a mixture of seven neutral amino acids, which resulted in partial recovery of polyribosomes, also tended to reverse the changes in ribosomal protein phosphorylation. Variations in the activities of ribonuclease enzymes in the cerebral cytosol were also observed under these conditions. Administration of phenylalanine increased the activities of cerebral ribonucleases, whereas subsequent treatment with the amino acid mixture partly reversed this effect. The results suggest that alterations in cerebral ribosomal protein phosphorylation, ribosome aggregation and ribosome function are interrelated in experimental hyperphenylalaninaemia.

Cambridge students training in the London clinical medical schools. Some inter-school differences in entry qualifications and final examination results

From data on the preclinical degree classifications and final M.B. results of 910 Cambridge students studying in London clinical medical schools, substantial differences between schools emerge. They have implications for the debate on the Flowers report.

Phosphorylation of multiple proteins of both ribosomal subunits in rat cerebral cortex in vivo. Effect of adenosine 3':5'-cyclic monophosphate

Investigations were carried out on the phosphorylation of ribosomal proteins in vivo in cerebral cortices of immature rats. Two-dimensional electrophoresis revealed that the cerebral 40S subunit contained at least four ribosomal proteins which were phosphorylated in animals given [32P]orthophosphate intracisternally. These proteins exhibited electrophoretic properties similar to those of the constitutive basic proteins S2, S3a, S5 and S6. The cerebral 60S subunit contained several proteins that were phosphorylated in vivo, including three basic proteins with electrophoretic mobilities similar to those of ribosomal proteins L6, L14 and L19. Four other proteins associated with the 60S subunit that were more acidic were also phosphorylated. Phosphorylated congeners of 40S and 60S ribosomal proteins could often be detected in distinct protein-stained spots on two-dimensional electrophoretograms. The cerebral S6 protein consisted of at least five distinct species in different states of phosphorylation. Administration of N6O-2' dibutyryl cyclic AMP increased the proportion of the more phosphorylated congeners of the S6 protein, but appeared to have little or no effect on phosphorylation of other cerebral ribosomal proteins. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine also stimulated S6-protein phosphorylation; N2O2'-dibutyryl cyclic GMP had no effect on this process. These observations indicate that several ribosomal proteins of both subunits are normally phosphorylated in rat cerebral cortex in situ. The results also suggest that selective and specific alterations in the phosphorylation state of the S6 ribosomal protein of the cerebral 40S subunit may accompany the production of cyclic AMP during neural activation.

Triglyceride integrated concentrations: effect of variation of source and amount of dietary carbohydrate

The effect of changes in the amount of dietary carbohydrate (45 or 65% of total energy) and in the source of carbohydrate (sucrose or corn syrup) on plasma triglyceride and cholesterol concentrations was studied in eight healthy males. Subjects ingested each of the four formula diets for 10 days in a latin square sequence. Diet-induced response was assessed by measurement of plasma lipid concentrations in blood obtained after overnight fast and by measurement of the mean plasma lipid concentrations--designated the integrated concentration--of blood obtained by 24 hr continuous blood withdrawal. The fasting plasma triglyceride concentration increased significantly during ingestion of the high carbohydrate diet (P less than 0.005) but was not significantly influenced by the source of carbohydrate calories. The 45% carbohydrate diets induced larger meal associated plasma triglyceride variation than 65% diets. Sucrose-containing diets induced significantly higher plasma triglyceride integrated concentrations than corn syrup diets, whether provided as 45% (P less than 0.05) or 65% (P less than 0.005) of total energy. Diet-induced changes in fasting or integrated plasma cholesterol concentration were minimal.

Technique of echographic examination of right ventricular wall thickness from the right sternal border

Right ventricular wall motion was readily accessible for echocardiographic recording along the right sternal border in 27 pediatric patients (age: 24 hrs--12 yrs). Right ventricular epicardial and endocardial wall motion could be recorded only at the right sternal border in 10 of these patients, emphasizing the need for a new, alternative examination site. Calculated measurements of right ventricular wall thickness recorded from both right and left sternal borders (7 pts) were similar (range of diff.=0--0.6 mm; mean of diff.=0.26 mm). Autopsy confirmation of right ventricular wall thickness was obtained in 2 patients. Epicardial motion could not be identified at the left sternal border in 10 patients. In these patients, right ventricular wall thickness was estimated by measuring from the inner chest wall to the endocardium. These measurements were compared to right ventricular wall thickness obtained from the right sternal border. Wall thickness obtained from the left sternal border was significantly underestimated in the absence of a definite epicardial interface (range of diff.=0.2--2.6 mm; mean of diff.=1.3 mm).

Acquisition of differentiative capacity in imaginal wing discs of Drosophila melanogaster

The wing discs from larvae undergoing the moult from 1st to 2nd instar are able to differentiate some parts of the adult wing when forced to undergo a premature metamorphosis. The first structures which differentiate are parts of the wing hinge and the wing blade. As development proceeds and older discs are forced through metamorphosis, the capacity to differentiate moves out both proximally and distally until gradually all of the derivatives of a mature wing disc are formed. Individual structures often differentiate from young discs in an incomplete form and pattern elements, such as bristles or sensilla, are added as older discs are tested.

Interactions between lysergic acid diethylamide and dopamine-sensitive adenylate cyclase systems in rat brain

Investigations were carried out on the interactions of the hallucinogenic drug, D-lysergic acid diethylamide (D-LSD), and other serotonin antagonists with catecholamine-sensitive adenylate cyclase systems in cell-free preparations from different regions of rat brain. In equimolar concentration, D-LSD, 2-brono-D-lysergic acid diethylamide (BOL), or methysergide (UML) strongly blocked maximal stimulation of adenylate cyclase activity by either norepinephrine or dopamine in particulate preparations from cerebral cortices of young adult rats. D-LSD also eliminated the stimulation of adenylate cyclase activity of equimolar concentrations of norepinephrine or dopamine in particulate preparations from rat hippocampus. The effects of this hallucinogenic agent on adenylate cyclase activity were most striking in particulate preparations from corpus striatum. Thus, in 10 muM concentration, D-LSD not only completely eradicated the response to 10 muM dopamine in these preparations but also consistently stimulated adenylate cyclase activity. L-LSD (80 muM) was without effect. Significant activation of striatal adenylate cyclase was produced by 0.1 muM D-LSD. Activation of striatal adenylate cyclase of either D-LSD or dopamine was strongly blocked by the dopamine-blocking agents trifluoperazine, thioridazine, chlorpromazine, and haloperidol. The stimulatory effects of D-LSD and dopamine were also inhibited by the serotonin-blocking agents, BOL, 1-methyl-D-lysergic acid diethylamide (MLD), and cyproheptadine, but not by the beta-adrenergic-blocking agent, propranolol. However, these serotonin antagonists by themselves were incapable of stimulating adenylate cyclase activity in the striatal preparations. Several other hallucinogens, which were structurally related to serotonin, were also inactive in this regard, e.g., mescaline, N,N-dimethyltryptamine, psilocin and bufotenine. Serotonin itself produced a small stimulation of adenylate cyclase activity in striatal preparations and, in relatively high concentration (100 muM), partially blocked the activation by 10 muM dopamine, but was without effect on the stimulation by 10 muM D-LSD. The present results indicate that serotonin antagonists, in general, are potent inhibitors of catecholamine-induced stimulation of adenylate cyclase systems in brain cell-free preparations. In addition, these results, coupled with earlier findings on the capacity of D-LSD to interact with serotonin-sensitive adenylate cyclase systems from rat brain23,24 and other neural systems16, strongly suggest that this hallucinogenic agent is capable of acting as an agonist at central dopamine and serotonin receptors, as well as functioning as an antagonist at dopamine, norepinephrine, and serotonin receptors in the brain.

Phosphorylation of ribosomal proteins in rat cerebral cortex in vitro

Incubation of cerebral cortical tissue from immature rats in the presence of [32P]orthophosphate resulted in similar rates of incorporation of radioactivity into the proteins of free and membrane-bound ribosomes. Incorporation of label into ribosomal proteins of both species continued actively for at least 3 hours. Since recovery of membrane-bound ribosomes from rat cerebral cortex is quite low, further analyses of the radioactive phosphoproteins were restricted to the free ribosome population. A significant fraction of the radioactivity which was precipitated with trichloroacetic acid was not removed by heating in trichloroacetic acid at 90 degrees or extracted with organic solvents and therefore was presumed to be covalently bound to protein. The radioactive phosphoryl groups present in the ribosomal proteins were mainly in ester linkages since they were readily removed by exposure to 1 N NaOH, relatively unaltered by 1N HCl, and unaffected by hydroxylamine. This conclusion was supported by the isolation of labeled o-phosphoserine and o-phosphothreonine residues from hydrolysates of ribosomal proteins. A significant fraction of the labeled phosphoproteins in the purified ribosomes appeared to be bound tightly to the ribosome structure since only 40% of the radioactivity could be removed by extraction of these ribosomes with 1 M KCl. Phosphorylation of proteins of cerebral monoribosomes was more rapid than the same process in polyribosomes from the same source. Eight radioactive phosphoprotein bands could be detected by electrophoresis of proteins obtained from unfractionated cerebral ribosomes on unidimensional polyacrylamide gels containing sodium dodecyl sulfate. The protein nature of these materials was confirmed by pronase digestion. Proteins of subribosomal particles isolated from the total free ribosomal population were labeled differentially. When dissociation was carried out in the presence of EDTA, the small subunit contained four radioactive phosphoprotein bands, whereas the large subunit contained five. Three of the radioactive phosphoprotein components of the small subunit were removed when dissociation of cerebral ribosomes which were previously washed with high salt media was carried out in the presence of puromycin and high salt. However, only the largest labeled phosphoprotein band of the large subunit was removed by this procedure. This component exhibited the same electrophoretic mobility as one of the radioactive phosphoprotein bands which was removed from the small subunit by high salt treatment..

Serotonin-sensitive adenylate cyclase activity of immature rat brain

Cell-free preparations from superior and inferior colliculi of very young rats (1-3 days old) contained adenylate cyclase systems which were highly responsive to serotonin. The response to serotonin declined markedly during early development and was very low at maturity. Adenylate cyclase activity in the 10,000 times g particulate fraction from colliculi of newborn rats was significantly stimulated by 0.05 muM serotonin. Half-maximal activation was produced with less than 1 muM serotonin. Maximal stimulation of collicular adenylate cyclase was about 80% above basal enzyme activity and occurred with approximately 50 muM serotonin. Tryptamine and several derivatives of serotonin produced responses which were comparable to that obtained with serotonin; 5-methoxytryptamine was uniformly the most active compound tested. Norepinephrine or dopamine produced much smaller increases in adenylate cyclase activity. Stimulation of collicular adenylate cyclase by serotonin was significantly but incompletely blocked by serotonin antagonists, including d-lysergic acid diethylamide (d-LSD), 2-bromo-d-lysergic acid diethylamide, methysergide, 1-methyl-8 beta-carbobenzyloxy-aminomethyl-10 alpha-ergoline and cyproheptadine. Chlorpromazine also produced partial blockade. In contrast, l-lysergic acid diethylamide, haloperidol, propranolol, phenoxybenzamine and morphine were ineffective as serotonin blocking agents. Of the compounds which produced a partial blockage of serotonin action, d-LSD, cyproheptadine and chlorpromazine were themselves capable of stimulating adenylate cyclase activity. These results are consisent with the existence of multiple receptors in rat brain which are capable of interacting with indoleamines.

Carcinoembryonic antigen in the urine of patients with urothelial carcinoma

Increased amounts of carcinoembryonic antigen (C.E.A.) or C.E.A.-like material are found in the urine of many patients with transitional cell carcinomas of the bladder, including those presumed to be at an early stage of development. It is suggested that measurement of urinary C.E.A. is of clinical diagnostic value in the detection and follow-up of urothelial carcinomas.

Activation of solubilized steroid-transforming enzymes of adrenal microsomal origin by serum proteins

The reactions which result in the conversion of pregnenolone to progesterone and of progesterone to deoxycorticosterone in undisrupted microsomal preparations from rat adrenal glands were stimulated by homologous serum. The active materials were shown to be firmly associated with serum proteins. The dialysable fraction of serum was either without effect on these transformations or was inhibitory. The enzyme systems involved were partially solubilized by exposure of the microsomal preparation to prolonged sonic treatment or to 1% Triton N-101. After either treatment, 35–40% of the original specific activity of the steroid 21-hydroxylase system responsible for the conversion of progesterone to deoxycorticosterone was found in the supernatant fraction after high-speed centrifugation. However, this solubilized system did not respond to serum preparations. The same procedures also resulted in a supernatant fluid which showed about 50–60% of the initial specific activity of the multi-enzyme system involved in the conversion of pregnenolone to progesterone. In these instances, the stimulatory effect of serum was retained or accentuated. Acetone powders prepared from the adrenal microsomal fraction were also active in the conversion of pregnenolone to progesterone and responded to serum with enhanced activity. Earlier observations that activation of steroid 21-hydroxylase by homologous rat serum was specific for the β-globulin fraction were confirmed in the present investigations. In contrast, stimulation of the conversion of pregnenolone to progesterone was apparently due principally to the albumin fraction. Albumin preparations from a number of other sources, as well as whole human serum protein, were also effective in this regard. The active protein preparations selectively stimulated 4-ene-3β-hydroxysteroid dehydrogenase activity, but did not activate 5-ene-3-oxosteroid isomerase in the microsomal fraction. This finding suggested that activation of 5-ene-3β-hydroxysteroid dehydrogenase was responsible for stimulation of progesterone synthesis from pregnenolone. The results indicate that the protein-bound factor in rat serum which was capable of stimulating the conversion of progesterone to deoxycorticosterone in microsomal preparations from rat adrenal glands was different from that which activates the conversion of pregnenolone to progesterone. Moreover, these diverse factors appeared to act by different mechanisms.