A comparison of the brain uptake of N-(cyclopropyl[11C]methyl)norbuprenorphine ([11C]buprenorphine) and N-(cyclopropyl[11C]methyl)nordiprenorphine ([11C]diprenorphine) in baboon using PET

Buprenorphine and diprenorphine were radiolabeled with 11C and their distributions in the baboon brain were studied using positron emission tomography (PET). Specific binding was demonstrated in the striatum (but not in the cerebellum) by pretreating the baboon with (-)naloxone. The absolute striatal uptakes and time courses were similar for these two radioligands but the ratio of radioactivity in the striatum to cerebellum in the baboon was higher for [11C]diprenorphine than for [11C]buprenorphine. Analysis of baboon plasma indicated that both [11C]diprenorphine and [11C]buprenorphine are rapidly metabolized. Analysis of radioactivity in mouse brain indicated that these two radioligands are stable to metabolic transformation. At 30 min after injection, 86-90% of extracted radioactivity was due to unchanged 11C-labeled radioligands. These results suggest that both [11C]diprenorphine and [11C]buprenorphine may be useful radioligands for studying opioid receptors in humans, although [11C]diprenorphine may be a better radioligand than [11C]buprenorphine for this purpose because of its more rapid clearance from the cerebellum.

Age-related decreases in muscarinic cholinergic receptor binding in the human brain measured with positron emission tomography (PET)

Muscarinic cholinergic M1 and M2 receptors in young and aged adult male volunteers were studied using [N-11C-methyl]-benztropine, a specific muscarinic cholinergic receptor ligand, and high resolution positron emission tomography (PET). A regionally specific pattern of decreased binding was observed in aged volunteers. Using two separate methods of data analysis, thalamic, hippocampal and cerebellar regions showed no decreases in the apparent specific binding of [N-11C-methyl]-benztropine while frontal, parietal, temporal and occipital cortices as well as the corpus striatum showed age related changes in binding that declined (in 82 yrs old subject) to about 50% of the value obtained from the youngest volunteer (19 yrs). These data suggest that regions high in muscarinic receptor density, the corpus striatum and the cortical mantle, show a greater rate of decline than those areas that have a relatively low number of muscarinic receptors. Furthermore, this study demonstrates the usefulness of PET and [N-11C-methyl]-benztropine for assessing age related regional changes in muscarinic cholinergic receptor binding in the living human brain.

Graphical analysis of reversible radioligand binding from time-activity measurements applied to [N-11C-methyl]-(-)-cocaine PET studies in human subjects

A graphical method of analysis applicable to ligands that bind reversibly to receptors or enzymes requiring the simultaneous measurement of plasma and tissue radioactivities for multiple times after the injection of a radiolabeled tracer is presented. It is shown that there is a time t after which a plot of integral of t0ROI(t')dt'/ROI(t) versus integral of t0Cp(t')dt'/ROI(t) (where ROI and Cp are functions of time describing the variation of tissue radioactivity and plasma radioactivity, respectively) is linear with a slope that corresponds to the steady-state space of the ligand plus the plasma volume,.Vp. For a two-compartment model, the slope is given by lambda + Vp, where lambda is the partition coefficient and the intercept is -1/[kappa 2(1 + Vp/lambda)]. For a three-compartment model, the slope is lambda(1 + Bmax/Kd) + Vp and the intercept is -[1 + Bmax/Kd)/k2 + [koff(1 + Kd/Bmax)]-1) [1 + Vp/lambda(1 + Bmax/Kd)]-1 (where Bmax represents the concentration of ligand binding sites and Kd the equilibrium dissociation constant of the ligand-binding site complex, koff (k4) the ligand-binding site dissociation constant, and k2 is the transfer constant from tissue to plasma). This graphical method provides the ratio Bmax/Kd from the slope for comparison with in vitro measures of the same parameter. It also provides an easy, rapid method for comparison of the reproducibility of repeated measures in a single subject, for longitudinal or drug intervention protocols, or for comparing experimental results between subjects. Although the linearity of this plot holds when ROI/Cp is constant, it can be shown that, for many systems, linearity is effectively reached some time before this. This analysis has been applied to data from [N-methyl-11C]-(-)-cocaine ([11C]cocaine) studies in normal human volunteers and the results are compared to the standard nonlinear least-squares analysis. The calculated value of Bmax/Kd for the high-affinity binding site for cocaine is 0.62 +/- 0.20, in agreement with literature values.

More evidence on women (and men) in the middle

A recent article by Rosenthal, Matthews and Marshall (1989) focused on two related questions: How typical is Brody's "woman in the middle" and how "normative" is parent care? This research builds on their work by presenting similar analyses for a somewhat larger probability sample of middle-aged women from a U.S. metropolitan area, by presenting parallel analyses for men in the same age groups, and by presenting data on more active measures for an expanded set of roles and role combinations not included in the original article. The four major roles analyzed by Rosenthal et al. (spouse, paid worker, adult child of aging parent, and parent) are found to be typical of those in their forties and early fifties, but each falls off rapidly after that point. Men are almost as likely to experience each of these as are women, and more likely to be married. When measures of more active involvement in these roles are examined, much smaller percentages of women or men are seen participating at any given age, and the combination of full-time work, active parenting, and helping or living with parents is uncommon. It is suggested that the situation described by Brody is not typical of middle-aged women or men in the U.S. today at any given time, but that collection of data on histories of caregiving is needed.

Effects of chronic cocaine abuse on postsynaptic dopamine receptors

To assess the effects of chronic cocaine intoxication on dopamine receptors in human subjects, the authors evaluated [18F]N-methylspiroperidol binding using positron emission tomography in 10 cocaine abusers and 10 normal control subjects. Cocaine abusers who had been detoxified for 1 week or less showed significantly lower values for uptake of [18F]N-methylspiroperidol in striatum than the normal subjects, whereas the cocaine abusers who had been detoxified for 1 month showed values comparable to those obtained from normal subjects. The authors conclude that postsynaptic dopamine receptor availability decreases with chronic cocaine abuse but may recover after a drug-free interval.

Acute effects of ethanol on regional brain glucose metabolism and transport

To evaluate the effects of ethanol in the human brain, we tested six normal subjects and six alcoholics using positron emission tomography and 2-deoxy-2-[18F]-fluoro-D-glucose (FDG) under baseline conditions and 24 hours later after ethanol administration (1 g/kg). Ethanol inhibited cortical and cerebellar glucose metabolism with relative sparing of the basal ganglia and corpus callosum. This inhibition was more pronounced in the alcoholics than in the controls. Measurement of the constants for glucose transport and utilization showed that decreased glucose metabolism was due to a reduction in glucose phosphorylation and not to a change of glucose transport into the tissue. The pattern of regional metabolic inhibition by alcohol paralleled the distribution of benzodiazepine receptors in the human brain.

Prophylaxis against hepatitis A for travel

OBJECTIVE

To develop a rational practice policy for prophylaxis against hepatitis A for travellers to high risk areas.

DESIGN

18 Month prospective study of consecutive patients who requested prophylaxis against hepatitis A.

SETTING

Inner city general practice.

SUBJECTS

104 Patients aged 15-61 (mean 30) assessed for risk factors for hepatitis A and put into groups depending on predictions from the risk factors of their immunity.

MAIN OUTCOME MEASURES AND RESULTS

All patients were screened for antibody to hepatitis A virus. Of 52 patients with no risk factors 47 had no antibody and were thus susceptible to hepatitis A. All 27 patients with major risk factors (having been brought up in an endemic area or with a history of jaundice) were immune. Of 25 patients with minor risk factors (a history of previous travel in high risk areas, drug abuse, having lived in a squat or travelled rough, or having lived with someone who had jaundice) 12 were immune (p less than 0.001, chi 2 test).

CONCLUSIONS

All travellers requesting prophylaxis against hepatitis A should be assessed for risk factors for previous exposure to hepatitis A. Those with no risk factors could be immunised with human normal immunoglobulin without screening. The remainder should be tested for hepatitis A antibody and those found to be susceptible should be immunised.

Manifestation of diabetes mellitus on mouse follicular and pre-embryo development: effect of hyperglycemia per se

Animal models of diabetes mellitus during pregnancy have repeatedly suggested that maternal hyperglycemia was teratogenic during organogenesis, and thus may contribute to diabetic teratogenesis. However, little attention has been focused on the effects of hyperglycemia on pre-organogenic development. In this report, we examine the effect of hyperglycemia (950 mg glucose/dL) on the development of mouse pre-embryos in vitro. B6C3F1 mice were superovulated with 5 U pregnant mare serum gonadotropin (PMSG) followed by 5 U human chorionic gonadotropin (hCG) 48 hours later. Two cell pre-embryos were recovered 48 hours later, pooled together, and randomly assigned to different treatment groups. Cultures were performed in HAM's F-10 media (Gibco, Long Island, NY) with 0.1% bovine serum albumin (BSA; Sigma, St. Louis, MO) BSA at 37 degrees C in an atmosphere of 5% CO2, 5% O2, and 90% N2 with 15 to 30 embryos per milliliter of culture fluid. Cultures were viewed daily at 24, 48, and 72 hours after culturing, with recording of the development. Compared with control pre-embryos (n = 216), embryos cultured in elevated glucose levels (950 mg/dL) (n = 226) demonstrated marked growth retardation as assessed both by (1) distribution of developmental stages at each observation point (24 hours, P less than .001; 48 hours, P less than .006; 72 hours, P less than .001); and (2) a difference in the average rank sums indicating a delay in maturation (P less than .005). In a second protocol group, pre-embryos were cultured in an equivalent amount of L-glucose; no impairment in development compared with controls was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Deriving a new nursing diagnosis through qualitative research: dysfunctional ventilatory weaning response

A secondary analysis was conducted on data originally collected using grounded theory methodology, to study nurses' perceptions of how they wean adult patients from mechanical ventilation. From this secondary analysis, a new nursing diagnosis was derived: dysfunctional ventilatory weaning response. This article discusses the rationale for the diagnostic label and describes salient characteristics and interventions related to the diagnosis.

Altered glucose metabolism in microvessels from patients with Alzheimer's disease

Microvessels isolated from temporal cortex of patients with Alzheimer's disease showed decreased uptake of glucose when compared with vessels from age-matched or young control subjects. This was due to decreased hexokinase activity in the Alzheimer samples, as determined by ion exchange chromatography. This finding was confirmed independently by determination of the phosphorylation constant for hexokinase, K3, using positron emission tomography. The results suggest that Alzheimer's disease may result from a global defect in brain energy metabolism.

Effect of norgestrel on development of mouse pre-embryos

The effect of synthetic progestins found in oral contraceptives has potential implications for developing embryos in women who receive oral contraceptives during early pregnancy. We assessed the effect of the progestin norgestrel on the developing pre-embryo. B3C6F1 mice were given 5 IU PMSG followed by 5 IU hCG 48h later. Studies were performed on pre-embryos recovered and pooled at both 24h (Group A) and 48h (Group B) post hCG. At each time period, they were randomly assigned to control or norgestrel (4.0 ng/ml) treatment. In a third study, pre-embryos collected 24h post hCG were cultured in the absence or presence of 8.0, 80.0, or 800 ng/ml norgestrel. Cultures were performed in Ham's F-10 media with 10% fetal calf serum at 37 degrees C in an atmosphere of 5% CO2, 5% O2 and 90% N2 with 15-30 embryos per 1 ml of culture fluid. At 24h, 48h and 72h post recovery, cultures were viewed, the appearance of embryos noted, and number of blastomeres recorded. Compared to control groups, analysis demonstrated no significant difference in the rate of development of control and norgestrel pre-embryos in any group at any time period (24h, 48h, or 72h post recovery). We conclude that norgestrel at the dose tested has no acute adverse morphological effects on development of mouse pre-embryos. This observation has potential clinical implications with regard to inadvertent use of norgestrel-containing oral contraceptives during early days of pregnancy, as well as consideration of the mechanism of action of norgestrel-containing "morning after" pills.

Regulation of poly(A) site selection in adenovirus

We have investigated the mechanisms involved in the early-to-late RNA-processing switch which regulates the mRNA species generated from the adenovirus major late transcription unit (MLTU). In particular, polyadenylation choice mechanisms were characterized by using a reconstructed adenovirus E1A gene as a site for insertion of MLTU poly(A) regulation signals (L1 and L3). Adenovirus constructs containing the variant poly(A) recognition elements were used to compare E1A poly(A) signal utilization with wild-type MLTU (L1 to L5) utilization. In both early and late stages of infection, either polyadenylation site (L1 or L3) is capable of being utilized when presented as the only operational poly(A) site. In an early infection, a virus which contains multiple elements presented in tandem (L13) uses the first poly(A) site, L1, preferentially (ratio of L1 to L3, 8:1) in both E1A and MLTU loci. Transcription termination is not involved in restricting the utilization of the downstream L3 site. In a late infection, when each of the five MLTU poly(A) sites is used, a switch also occurs for the E1AL13 construct, with utilization of both the L1 and L3 poly(A) sites. The switch from early to late was not the result of altered processing factors in the late infection, as demonstrated by superinfecting the E1AL13 construct into cells which had already entered a late stage of infection. The superinfecting virus gave an L1-only phenotype; therefore, a cis mechanism is involved in adenovirus poly(A) regulation.

Gender differences in family support: is there a payoff?

National data for respondents over age 65 revealed that, although women are less likely to be living with a spouse, living arrangements of unmarried women and men are similar. Women live closer to children, receive more phone calls, have marginally more contact but do not receive more mail. Women's receipt of more informal assistance is largely explained by greater need levels, particularly for the unmarried. These findings are discussed in relation to women's roles as family caretaker and kinkeeper at earlier life cycle stages.

Mapping cocaine binding sites in human and baboon brain in vivo

The first direct measurements of cocaine binding in the brain of normal human volunteers and baboons have been made by using positron emission tomography (PET) and tracer doses of [N-11C-methyl]-(-)-cocaine ([11C]cocaine). Cocaine's binding and release from brain are rapid with the highest regional uptake of carbon-11 occurring in the corpus striatum at 4-10 minutes after intravenous injection of labeled cocaine. This was followed by a clearance to half the peak value at about 25 minutes with the overall time course paralleling the previously documented time course of the euphoria experienced after intravenous cocaine administration. Blockade of the dopamine reuptake sites with nomifensine reduced the striatal but not the cerebellar uptake of [11C]cocaine in baboons indicating that cocaine binding is associated with the dopamine reuptake site in the corpus striatum. A comparison of labeled metabolites of cocaine in human and baboon plasma showed that while cocaine is rapidly metabolized in both species, the profile of labeled metabolites is different, with baboon plasma containing significant amounts of labeled carbon dioxide, and human plasma containing no significant labeled carbon dioxide. These studies demonstrate the feasibility of using [11C]cocaine and PET to map binding sites for cocaine in human brain, to monitor its kinetics, and to characterize its binding mechanism by using appropriate pharmacological challenges.

Mechanistic positron emission tomography studies: demonstration of a deuterium isotope effect in the monoamine oxidase-catalyzed binding of [11C]L-deprenyl in living baboon brain

The application of positron emission tomography (PET) to the study of biochemical transformations in the living human and animal body requires the development of highly selective radiotracers whose concentrations in tissue provide a record of a discrete metabolic process. L-N-[11C-methyl]Deprenyl ([11C]L-deprenyl), a suicide inactivator of monoamine oxidase (MAO) type B, has been developed as a radiotracer for mapping MAO B in the living human and animal brain. In this investigation, [11C]L-deprenyl (1) and [11C]L-deprenyl-alpha, alpha-2H2 (2) have been compared in three different baboons by PET measurement of carbon-11 uptake and retention in the brain and the measurement of the amount of unchanged tracer in the arterial plasma over a 90-min time interval. For one baboon, N-[11C-methyl-2H3]L-deprenyl (3) was also studied. Kinetic parameters calculated using a three-compartment model revealed a deuterium isotope effect of 3.8 +/- 1.1. Comparison of the two tracers (1 and 2) in mouse brain demonstrated that deuterium substitution significantly reduced the amount of radioactivity bound to protein. HPLC and GLC analysis of the soluble radioactivity in mouse brain after injection of [11C]L-deprenyl showed the presence of [11C]methamphetamine as a major product along with unidentified labeled products. Sodium dodecyl sulfate-polyacrylamide electrophoresis with carbon-14-labeled L-deprenyl showed that a protein of molecular weight 58,000 was labeled. These results establish that MAO-catalyzed cleavage of the alpha carbon-hydrogen bond on the propargyl group is the rate limiting (or a major rate contributing) step in the retention of carbon-11 in brain and that the in vivo detection of labeled products in brain after the injection of [11C]L-deprenyl provides a record of MAO activity.

A poly(A) addition site and a downstream termination region are required for efficient cessation of transcription by RNA polymerase II in the mouse beta maj-globin gene

Sequence elements within the mouse beta maj-globin transcription unit required for efficient termination of transcription by RNA polymerase II have been delineated. To facilitate nascent-chain analysis of termination, the DNA segment in which transcription ceases was introduced into the adenovirus chromosome within its E1A transcription unit. Two beta-globin DNA elements were required to effect efficient termination: an upstream sequence that includes two poly(A) addition signals and a downstream region previously shown to be where RNA synthesis stops. The role of poly(A) addition in termination was established by introduction of several single base pair substitutions into the AATAAA polyadenylylation motifs. These mutations inhibited both polyadenylylation and termination within the beta-globin DNA segment. Therefore, poly(A) addition appears to be a prerequisite for efficient termination.

Serial PET studies of human cerebral malignancy with [1-11C]putrescine and [1-11C]2-deoxy-D-glucose

Serial PET measurements of [1-11C]putrescine ([11C]PUT) uptake and glucose metabolic rate (GMR) using [1-11C]2-deoxy-D-glucose ([11C]2DG) were made on eight human subjects with a radiological and, in most cases, pathological diagnosis of primary or metastatic brain tumor. Blood-to-brain influx constants (Ki) were calculated for [11C]PUT. Tumor uptake of 11C after [11C]PUT injection was unidirectional peaking at 15 min. The mean +/- s.d. Kis for [11C]PUT for tumor and normal brain tissue were 0.78 +/- 0.045 and 0.024 +/- 0.007 ml cc-1 min-1, respectively (average of ratio, 3.11) whereas the ratio of GMR for tumor and normal brain tissue was 1.2 +/- 0.5. The mean Ki for four active, high grade astrocytomas was 0.098 +/- 0.030 in contrast to 0.027 +/- 0.008 ml cc-1 min-1 for two patients with low grade astrocytoma. Active high grade astrocytomas also showed marked CT contrast enhancement and regional glucose hypermetabolism. In one subject with brain metastases, both [11C]PUT and GMR correlated with a declining clinical picture in repeated studies over a 4-mo period. PET studies with [11C]PUT provide a better signal:noise ratio than GMR measurements, are useful for locating small glycolytically hypometabolic tumors and, when used in longitudinal studies in a single subject, appear to provide an index of degree of malignancy.

Mapping human brain monoamine oxidase A and B with 11C-labeled suicide inactivators and PET

The regional distributions of monoamine oxidase (MAO) types A and B have been identified in human brain in vivo with intravenously injected 11C-labeled suicide enzyme inactivators, clorgyline and L-deprenyl, and positron emission tomography. The rapid brain uptake and retention of radioactivity for both 11C tracers indicated irreversible trapping. The anatomical distribution of 11C paralleled the distribution of MAO A and MAO B in human brain in autopsy material. The corpus striatum, thalamus, and brainstem contained high MAO activity. The magnitudes of uptake of both [11C]clorgyline and L-[11C]deprenyl were markedly reduced in one subject treated with the antidepressant MAO inhibitor phenelzine. A comparison of the brain uptake and retention of the 11C-labeled inactive (D-) and active (L-) enantiomers of deprenyl showed rapid clearance of the inactive enantiomer and retention of the active enantiomer within MAO B-rich brain structures, in agreement with the known stereoselectivity of MAO B for L-deprenyl. Prior treatment with unlabeled L-deprenyl prevented retention of L-[11C]deprenyl. Thus, suicide enzyme inactivators labeled with positron emitters can be used to quantitate the distribution and kinetic characteristics of MAO in human brain structures.

Kinetic modeling of receptor-ligand binding applied to positron emission tomographic studies with neuroleptic tracers

Positron emission tomography (PET) with labeled neuroleptics has made possible the study of neurotransmitter-receptor systems in vivo. In this study we investigate the kinetics of the 3,4-dihydroxyphenylethylamine (dopamine) receptor-ligand binding using PET data from a series of experiments in the baboon with the 18F-labeled drugs spiperone, haloperidol, and benperidol. Models used to describe these systems are based on first-order kinetics which applies at high specific activity (low receptor occupancy). The parameters governing the uptake and loss of drug from the brain were found by fitting PET data from regions with little or no receptor concentration (cerebellum) and from experiments in which specific binding was blocked by pretreatment with the drug (+)-butaclamol. Receptor constants were determined by fitting data from receptor-containing structures. Correcting the arterial plasma activities (the model driving function) for the presence of drug metabolites was found to be important in the modeling of these systems.

In vivo identification of sequence elements required for normal function of the adenovirus major late transcriptional control region

A series of adenovirus type 5 variants were constructed to identify the sequence elements which comprise the major late transcriptional control region in the context of the viral chromosome. The variant chromosomes carried a second copy of DNA sequence derived from the region surrounding the major late mRNA cap site. The reiterated segments replaced the normal transcriptional control region of the E1A gene. By monitoring the rate of E1A transcription subsequent to infection with the variants, it was possible to evaluate the capabilities of the substituted major late elements. A segment derived from -55 to +33 (relative to the major late cap site at +1) functioned for early transcription, in the presence of the E1A enhancer domain, but failed to direct enhanced levels of activity late after infection. A segment from -122 to +33 directed both early and enhanced late transcription. The rate of late E1A transcription directed by this element was about 40% of that displayed by the major late control region at its normal position. Inclusion of additional upstream sequences (to -565) did not increase late transcription rates. Thus, function of the adenovirus major late control region.

Disposition kinetics of cefamandole during continuous ambulatory peritoneal dialysis

Cefamandole disposition kinetics were examined in six male subjects with renal impairment who were undergoing continuous ambulatory peritoneal dialysis. Creatinine clearance values ranged from less than 1 to 11 ml/min. Cefamandole was given as a 1-g intravenous dose infused over 30 min. Cefamandole concentrations were determined in serum, urine, and dialysis fluid by a high-performance liquid chromatographic method. The following average parameter values were obtained (range): half-life, 6.1 h (4.6 to 9.7); systemic clearance, 21.9 ml/min (8.4 to 35.5); renal clearance, 11.5 ml/min (0.03 to 22.3); dialysis clearance, 0.92 ml/min (0.7 to 1.3); nonrenal clearance, 12.2 ml/min (2.9 to 27.0); volume of distribution, 0.18 liter/kg (0.09 to 0.25); steady-state volume of distribution, 0.17 liter/kg (0.09 to 0.24). Approximately 5% of the dose was dialyzed (range, 2.8 to 8.3), indicating that there is no need to supplement a dosing regimen of cefamandole due to loss by dialysis. There was a positive correlation between creatinine clearance and the terminal elimination rate constant of cefamandole (r2 = 0.41) and cefamandole renal clearance (r2 = 0.83).

The adenovirus E1B-55K transforming polypeptide modulates transport or cytoplasmic stabilization of viral and host cell mRNAs

The adenovirus type 5 mutant H5dl338 lacks 524 base pairs within early region 1B. The mutation removed a portion of the region encoding the related E1B-55K and -17K polypeptides but did not disturb the E1B-21K coding region. The virus can be propagated in 293 cells which contain and express the adenovirus type 5 E1A and E1B regions, but it is defective for growth in HeLa cells, in which its final yield is reduced about 100-fold compared with the wild-type virus. The mutant also fails to transform rat cells at normal efficiency. The site of the dl338 defect was studied in HeLa cells. Early gene expression and DNA replication appeared normal. Late after infection, mRNAs coded by the major late transcription unit accumulated to reduced levels. At a time when transcription rates and steady-state nuclear RNA species were normal, the rate at which late mRNA accumulated in the cytoplasm was markedly reduced. Furthermore, in contrast to the case with the wild type, transport and accumulation of cellular mRNAs continued late after infection with dl338. Thus, the E1B product appears to facilitate transport and accumulation of viral mRNAs late after infection while blocking the same processes for cellular mRNAs.

Cell-type-specific synthesis of murine immunoglobulin mu RNA from an adenovirus vector

The mouse immunoglobulin heavy-chain mu constant region gene was cloned into the early region 1B of an adenovirus type 5 vector to allow reproducible kinetics of expression of the mu gene in the presence of continuous host protein synthesis after infection by the recombinant. The immunoglobulin-adenovirus recombinant is helper independent in infecting human fibroblastic and B- and T-cell lines and expresses mu in a cell-type-specific manner. By Northern blot analysis, correctly polyadenylated and spliced E1B-mu S and E1B-mu m mRNAs are found to be equally abundant at steady state in fibroblasts. In contrast, and appropriately, only E1B-mu S mRNAs accumulate in a lambda light-chain-secreting myeloma cell line. Analysis of nascent transcripts pulse labeled in isolated nuclei demonstrates equimolar polymerase loading throughout the mu region in all cell types infected by mu-Ad. Thus, correct polyadenylation and splicing of E1B-mu S and E1B-mu m in fibroblasts does not require transcription termination in the region separating the mu S and mu m polyadenylation sites. Furthermore, differential expression of mu transcripts in the background of myeloma cells is regulated at the level of RNA processing and does not require the presence of the immunoglobulin heavy-chain enhancer or promoter element.

Transcription termination within the E1A gene of adenovirus induced by insertion of the mouse beta-major globin terminator element

In induced erythroleukemia cells, transcription of the beta-globin gene terminates in a region 600-1500 nucleotides downstream of the poly(A) site. To determine whether this region of the mouse DNA functions to terminate transcription when moved to another genomic site, portions of the putative termination region have been inserted into the E1A transcription unit of the adenovirus (type 5) chromosome. Analysis of RNA labeled either in isolated nuclei or in whole cells early after infection with reconstructed viruses indicated that transcription is terminated if the inserted DNA is oriented in the same direction as in the beta-globin transcription unit and contains the globin poly(A) site plus an additional 1395 nucleotides downstream. In addition to halting transcription within the E1A unit, the insertion of the terminator region had a negative cis effect on the E1B transcription unit, which normally initiates 363 bp downstream of the site of the globin insert. The E1B transcription unit was the only early gene affected, and complementation of the terminator virus with a wild-type E1A gene did not restore transcription of the E1B gene.

Comparison of three 18F-labeled butyrophenone neuroleptic drugs in the baboon using positron emission tomography

The butyrophenone neuroleptics spiroperidol, benperidol, and haloperidol were radiolabeled with fluorine-18 and studied in baboon brain using positron emission transaxial tomography (PETT). Pretreatment of the baboon with a high pharmacological dose of (+)-butaclamol reduced the specifically bound component of radioactivity distribution in the striatum to approximately the radioactivity distribution found in the cerebellum. Comparative studies of brain distribution kinetics over a 4-h period indicated that either [18F]spiroperidol or [18F]benperidol may be suitable for specific labeling of neuroleptic receptors. In an 8-h study with [18F]spiroperidol, striatal radioactivity did not decline, suggesting that spiroperidol either has a very slow dissociation rate or that it binds irreversibly to these receptors in vivo. [18F]Haloperidol may not be suitable for in vivo PETT studies, because of a relatively high component of nonspecific distribution and a faster dissociation from the receptor. Analysis of 18F in plasma after injection of [18F]spiroperidol indicated rapid metabolism to polar and acidic metabolites, with only 40% of the total radioactivity being present as unchanged drug after 30 min. Analysis of the metabolic stability of the radioactively labeled compound in rat striatum indicated that greater than 95% of [18F]spiroperidol remains unchanged after 4 h.

Deletion of the gene encoding the adenovirus 5 early region 1b 21,000-molecular-weight polypeptide leads to degradation of viral and host cell DNA

The adenovirus 5 mutant H5dl337 lacks 146 base pairs within early region 1B. The deletion removes a portion of the region encoding the E1B 21,000-molecular-weight (21K) polypeptide, but does not disturb the E1B-55K/17K coding region. The virus is slightly defective for growth in cultured HeLa cells, in which its final yield is reduced ca. 10-fold compared with wild-type virus. The mutant displays a striking phenotype in HeLa cells. The onset of cytopathic effect is dramatically accelerated, and both host cell and viral DNAs are extensively degraded late after infection. This defect has been described previously for a variety of adenovirus mutants and has been termed a cytocidal (cyt) phenotype. H5dl337 serves to map this defect to the loss of E1B-21K polypeptide function. In addition to its defect in the productive growth cycle, H5dl337 is unable to transform rat cells at normal efficiency.

Mapping brain neuroleptic receptors in the live baboon

An experimental strategy for external detection of specific neuroleptic receptors in living brain using positron emission transaxial tomography (PETT) and [11C]spiroperidol was applied to the mapping of brain neuroleptic receptors in the live baboon. A double injection of [11C]spiroperidol with an intervening time interval for carbon-11 decay and an intervening dose of (+)-butaclamol to block specific neuroleptic receptors produced two sets of PETT scans which were subtracted to produce a three-dimensional map of relative regional binding of neuroleptic receptors in the baboon brain. Sixty-five percent of the total radioactivity in the striatum was bound to neuroleptic receptors at 65 min after injection.

Adenovirus tripartite leader sequence enhances translation of mRNAs late after infection

A series of adenovirus type 5 variants was constructed to probe the function of the tripartite leader sequence, a 200-nucleotide, 5' noncoding sequence carried on the majority of late viral mRNAs. Recombinant plasmids were constructed that carried the major late transcriptional control region followed by portions of the tripartite leader sequence fused to the E1A coding region. These modified E1A genes were then rebuilt into intact viral chromosomes, replacing the corresponding wild-type region. The leader segments had no effect on the translation of E1A mRNAs early after infection, but the tripartite leader significantly enhanced (5-fold) the efficiency with which the mRNAs were translated late after infection.

An economic model of general practice

The public perceives that doctors earn too much, while general practitioners complain that their income is dwindling . In the absence of reliable data on doctors' incomes, it is impossible to determine whether medical fees are set appropriately, and what effects Medicare might have on general practice. An economic model of practice, using estimates of income and expenditure derived from specified assumptions, was constructed. Then, the effects of changes in various parameters of the model were examined in turn to show how economic forces are likely to affect the behaviour of doctors. It is shown that a general practitioner working at a moderate rate during a normal working week will earn a low income under current schedule fees. Some implications of these findings for practitioners, fee setting, and the public are explored.

A Monte Carlo simulation of Compton scattering in positron emission tomography

A Monte Carlo technique was used to simulate some of the important physical processes involved in the coincidence detection of gamma rays by a positron emission tomograph. The major effect considered here is the detection of Compton scattered gamma rays as coincidence counts. The Compton scattering of gamma rays in a H2O filled phantom was simulated using the Klein-Nishina cross section. Results obtained in the form of profiles of activity were compared to a model which represents scatter as the convolution of the true signal with an exponential.

Compartmental pressure measurements: an experimental investigation using the slit catheter

A new catheter employing a different technique to monitor compartmental pressure has been developed. The accuracy of the catheter was compared to a wick catheter and to the needle manometer technique for monitoring compartmental pressure. The slit catheter is the most accurate of the three techniques for continuous pressure monitoring for periods of up to 24 hours in the experimental canine model. The slit catheter is as accurate as the wick catheter for pressure measurements from 0 through 10 mm Hg. The needle technique has proven to be the least accurate of the three.