Graphical, kinetic, and equilibrium analyses of in vivo [123I] beta-CIT binding to dopamine transporters in healthy human subjects

The in vivo kinetics of the dopamine (DA) transporter probe 123I-labeled 2 beta-carboxymethoxy-3 beta-(4-iodophenyl) tropane ([123I] beta-CIT) in striatum was investigated with single-photon emission computerized tomography (SPECT) in five healthy human subjects. The aim of this study was to derive an adequate measure of the DA transporter density that would not be affected by regional cerebral blood flow or peripheral clearance of the tracer. SPECT data were acquired on the day of injection (day 1) from 0 to 7 h and on the following day (day 2) from 19 to 25 h. Arterial sampling on day 1 was used to measure the input function. Graphical, kinetic, and equilibrium analyses were evaluated. Graphical analysis of day 1 data, with the assumption of negligible dissociation of the tracer-receptor complex (k4 = 0), was found to be blood flow-dependent. A three-compartment kinetic analysis of day 1 data were performed using a three (k4 = 0)- and a four (k4 > 0)-parameter model. The three-parameter model estimated the konBmax product at 0.886 +/- 0.087 min-1. The four-parameter model gave a binding potential (BP) of 476 ml g-1, a value consistent with in vitro measurements. The stability of the regional uptake on day 2 allowed direct measurement of the specific to nonspecific equilibrium partition coefficient (V3" = k3/k4 = 6.66 +/- 1.54). Results of day 1 kinetic analysis and day 2 equilibrium analysis were well correlated among subjects. Simulations indicated that the error associated with the day 2 equilibrium analysis was acceptable for plasma tracer terminal half-lives > 10 h. We propose the equilibrium analysis on day 2 as the method of choice for clinical studies since it does not require multiple scans or the measurement of the arterial plasma tracer concentrations.

Feeding the wound: nutrition and wound care

The nutritional health of the individual can determine the outcome of wound management. Frequent nutritional assessments must be performed in order to detect patients with malnutrition or at risk of malnutrition. Energy requirements must be calculated for those deemed to be malnourished or at risk of malnourishment. Early intervention is paramount to ensure that wound healing occurs unimpeded. The use of glutamine and arginine supplements enhances wound healing and should be increased. Nutritional care is cost-effective.

Whole-body biodistribution, radiation absorbed dose and brain SPECT imaging with iodine-123-beta-CIT in healthy human subjects

SPECT imaging with 123I-labeled methyl 3 beta-(4-iodophenyl)tropane-2 beta-carboxylate ([123I]beta-CIT) in nonhuman primates has shown brain striatal activity, which primarily reflects binding to the dopamine transporter. The biodistribution and calculated radiation-absorbed doses of [123I]beta-CIT administered to eight healthy subjects were measured with attention to the accurate determination of organ time-activity data.

METHODS

Whole-body transmission images were obtained with a scanning line source for attenuation correction of the emission images. Following administration of 92.5 +/- 22.2 MBq (2.5 +/- 0.6 mCi) of [123I]beta-CIT, subjects were imaged with a whole-body imager every 30 min for 3 hr, every 60 min for the next 3 hr and at 12, 24 and 48 hr postinjection. Regional body conjugate counts were converted to microcuries of activity, with a calibration factor determined in a separate experiment using a distributed source of 123I.

RESULTS

The peak brain uptake represented 14% of the injected dose, with 2% of the activity approximately overlying the striatal region. Highest radiation-absorbed doses were to the lung (0.1 mGy/MBq, 0.38 rads/mCi), liver (0.087 mGy/MBq, 0.32 rads/mCi) and lower large intestine (0.053 mGy/MBq, 0.20 rads/mCi).

CONCLUSIONS

Iodine-123-beta-CIT is a promising SPECT agent for imaging of the dopamine transporter in humans with favorable dosimetry and high brain uptake.

Sex hormones regulate ABR latency

In an effort to characterize more completely the influence of sex hormones on auditory brainstem response (ABR) latency, we evaluated the ABRs of normal male and female subjects and women with previously diagnosed endocrinologic syndromes. We describe ABR latency results from the following subjects: five normal males, nine normally cycling females on no hormonal therapy, nine females using oral contraceptive pills, five females with premature ovarian failure (POF) undergoing cyclic estrogen-progesterone replacement therapy, and five hyperandrogenized females with polycystic ovarian disease (PCOD) treated with the gonadotropin-releasing hormone agonist, Lupron depot, to suppress ovarian steroid production. All subjects were between 23 and 40 years of age. Serum levels of estradiol, progesterone, testosterone, prolactic, and gonadotropins (lutienizing hormone and follicle stimulating hormone) were measured to document the hormonal status of each of the subjects at the time of the ABR evaluation. Normal cycling females and females with POF underwent ABR testing during different phases of the same cycle. Male subjects and females using birth control pills were studied four times in the same month at 1-week intervals. Females with PCOD were also studied four times; baseline and then at 2-week intervals after the initiation of Lupron depot therapy. Increased ABR wave V peak latencies were found to be associated with elevated levels of estrogen or testosterone. We have previously reported a lengthening of ABR wave V peak latencies coincident with peak estrogen levels during the female cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Single photon emission computed tomographic imaging demonstrates loss of striatal dopamine transporters in Parkinson disease

[123I][(1R)-2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane] ([123I]beta-CIT) labels dopamine transporters and is, therefore, a marker of neurons that degenerate in Parkinson disease. Single photon emission computed tomography imaging with [123I]beta-CIT showed that radioactivity in striatal regions in healthy subjects increased during a 2-day imaging study, whereas that in Parkinsonian patients peaked earlier at reduced levels relative to healthy subjects. Kinetic analyses of radioactivity in plasma and brain suggest that this decrease was due to an approximately 65% loss of target sites in patients compared with healthy subjects; greater losses occurred in putamen than in caudate. All patients showed lateralized differences in striatal uptake, with greater losses in the striatum contralateral to the side of the body with initial symptoms. These preliminary results suggest that [123I]beta-CIT is a marker for the loss of striatal dopamine terminals in patients with Parkinson disease. Single photon emission computed tomographic imaging with [123I]beta-CIT may be useful for early diagnosis of the disorder, for monitoring the progression of the disease, and for distinguishing the idiopathic disorder from other Parkinsonian syndromes with more widespread pathology.

Nursing a teenager with burns

Development of body image is an integral part of a teenager's psychological growth. Burned teenagers experience great difficulty in readjusting psychosocially after injury as they have not yet formed their own self-concept and sense of worth. Burns patients experience a range of psychological problems as a consequence of disfigurement. These include depression, phobias, insomnia, sexual problems, high divorce rates, juvenile delinquency and impaired employment or academic status. Few nursing research articles have addressed the psychosocial problems of burns patients. Even if nurses are not skilled in counselling they must be able to recognize problems and refer patients to colleagues with the appropriate skills.

The effects of malnutrition in hospital

Between 30 and 50% of inpatients suffer some degree of malnutrition and as a result have a higher risk of complications and higher mortality than well-nourished patients. Nurses have a fundamental role in combating and preventing malnutrition, yet lack knowledge and understanding of the problem. This article describes the effects of malnutrition and discusses the nurse's role in the provision of nutritional care.

Cyclic steroid replacement alters auditory brainstem responses in young women with premature ovarian failure

To determine the independent contributions of estradiol and progesterone to the auditory brainstem response (ABR) latency changes associated with the menstrual cycle, we obtained ABRs on young women with premature ovarian failure who were undergoing cyclic hormone replacement therapy (HRT). We evaluated the influence of cyclic HRT on the ABRs of young women in three controlled phases of the same replacement cycles: 1) no steroid replacement, 2) estrogen-only replacement (E2-only), and 3) estrogen-plus-progesterone replacement (E2-plus-P). A significantly lengthening of wave V peak latency and I-V interpeak interval was found during E2-only replacement. Despite equivalent circulating estradiol levels, both wave V peak latencies and wave I-V interpeak intervals significantly decreased during the E2-plus-P replacement phase as compared to the E2-only replacement phase. These findings are compatible with the hypothesis that estradiol potentiates secretion of the inhibitory neurotransmitter gamma-amino-butyric acid (GABA) at auditory nerve synapses, leading to delayed synaptic conduction time. Progesterone is known to blunt E2-potentiated GABA release and may antagonize its prolongation of wave V latency.

The Ontario HIV seroprevalence study of childbearing women: results from the first year of testing

The Ontario HIV Seroprevalence Study of Childbearing Women is an unliked anonymous seroprevalence study designed according to the well-established ethical and legal guidelines for such studies. Commencing in November, 1989, randomly selected neonatal heelprick specimens were tested for the presence of HIV antibodies after all identifying information had been permanently and irrevocably unlinked from the specimens. During the first year of the study 94,119 (approximately 60% of all submitted specimens) were tested. Twenty-six specimens which were repeatedly reactive by EIA were confirmed as positive for an overall crude seroprevalence rate of 2.8 per 10,000 women having live births (95% CI: 1.8-4.1). Twenty-five of the 26 confirmed seropositive results came from babies born in hospitals in the Metropolitan Toronto, Ottawa-Carlton, or Hamilton-Peel-Halton regions.

Long term psychotherapy training in residency: influences on therapy and training

The authors discuss the changing role of psychotherapy training and the impact of rotations on long term psychotherapy in psychiatric residency. A conceptual model for a long term psychotherapy program for residents is presented, and a case example illustrates the influence of changes in setting, supervisors and in the resident-therapist's way of thinking have on the process of psychotherapy. The educational value of long term patient contact and the opportunity to use apparent obstacles in residency training as catalysts for growth and the opportunity to learn about psychotherapy are emphasized.

Clostridium difficile-associated diarrhoea

During the course of 1 year, Clostridium difficile was isolated from 145 (4 per cent) of 3591 faecal specimens submitted to a hospital routine bacteriology laboratory. These C. difficile positive specimens came from 95 patients or 10.99 per cent of 864 patients investigated for suspected gastroenteritis. In a control population of 318 persons C. difficile was isolated from only 10 of them or 3.1 per cent; this difference was statistically significant. We conclude that as this increase in the isolation of C. difficile from patients with diarrhoea is significant and is about as frequent as that of Campylobacter spp., faecal specimens submitted for routine bacteriology should also be cultured for C. difficile . As with diarrhoea caused by other enteric pathogens, most C. difficile -associated episodes of diarrhoea are mild and spontaneously reversible but approximately 20 per cent of patients have prolonged diarrhoea and may benefit from treatment.

Biochemical screening of hospitalized geriatric patients

Blood specimens were collected from 50 hospitalized geriatric patients with a range of chronic diseases. Analyses were conducted for 12 plasma components. Additional tests were performed on patients with abnormal results in the first tests. Of the 50 patients, 21 (42 per cent) had biochemical abnormalities, often unexpected on the basis of current diagnoses. It is suggested that routine biochemical screening should be conducted on geriatric patients at regular intervals.