Quantitative [18F]fluorodopa/PET and histology of fetal mesencephalic dopaminergic grafts to the striatum of MPTP-poisoned minipigs

The functional restoration of the dopamine innervation of striatum in MPTP-poisoned Göttingen minipigs was assessed for 6 months following grafting of fetal pig mesencephalic neurons. Pigs were assigned to a normal control group and a MPTP-poisoned group, members of which received no further treatment, or which received bilateral grafts to the striatum of tissue blocks harvested from E28 fetal pig mesencephalon with and without immunosuppressive treatment after grafting, or with additional co-grafting with immortalized rat neural cells transfected to produce GDNF. In the baseline condition, and again at 3 and 6 months postsurgery, all animals were subjected to quantitative [18F]fluorodopa PET scans and testing for motor impairment. At the end of 6 months, tyrosine hydroxylase (TH)-containing neurons were counted in the grafts by stereological methods. The MPTP poisoning persistently reduced the magnitude of k3(D), the relative activity of DOPA decarboxylase in striatum, by 60%. Grafting restored the rate of [18F]fluorodopa decarboxylation to the normal range, and normalized the scores in motor function. The biochemical and functional recovery was associated with survival of approximately 100,000 TH-positive graft neurons in each hemisphere. Immunosuppression did not impart a greater recovery of [18F]fluorodopa uptake, nor were the number of TH-positive graft neurons or the volumes of the grafts increased in the immunosuppressed group. Contrary to expectation, co-grafting of transfected GDNF-expressing HiB5 cells, a rat-derived neural cell line, tended to impair the survival of the grafts with the lowest values for graft volumes, TH-positive cell numbers, behavioral scores, and relative DOPA decarboxylase activity. From the results we conclude that pig ventral mesencephalic allografts can restore functional dopamine innervation in adult MPTP-lesioned minipigs.

The Danish PET/depression project: clinical symptoms and cerebral blood flow. A regions-of-interest analysis

OBJECTIVE

We wanted to explore associations between clinical symptoms of depression and the blood flow to specific regions of the brain. Furthermore, we wanted to compare the regions-of-interest (ROI) method with the functions-of-interest (FOI) approach.

METHOD

The resting blood flow to 42 ROI in the brain was obtained with positron emission tomography (PET) imaging in 42 representative in-patients with major depression and 47 matched healthy controls.

RESULTS

The patients had increased blood flow to hippocampus, cerebellum, anterior cingulate gyrus, and the basal ganglia. A strong negative correlation was found between the degree of psychomotor retardation of the patients and the blood flow to the dorsolateral and supraorbital prefrontal cortices. The total Hamilton score was correlated with the blood flow to the hippocampus.

CONCLUSION

Our findings support the notion that depressed patients have disturbances in the loops connecting the frontal lobes, limbic system, basal ganglia, and cerebellum.

MR-based statistical atlas of the Göttingen minipig brain

Thedomestic pig is increasingly being used as an experimental model for brain imaging studies with positron emission tomography (PET). The recording of radiotracer uptake by PET gives functional and physiological information, but with poor spatial resolution. To date, anatomical regions of interest in pig brain have been defined in MR images obtained for each individual animal, because of the lack of a standard stereotaxic coordinate system for the pig brain. In order to define a stereotaxic coordinate system, we coregistered T1-weighted MR images from 22 male Göttingen minipigs and obtained a statistically defined surface rendering of the average minipig brain in which stereotaxic zero is defined by the position of the pineal gland. The average brain is now used as a target for registration of dynamic PET data, so that time-activity curves can be extracted from standard volumes of interest. In order to define these volumes, MR images from each individual pig were manually segmented into a total of 34 brain structures, including cortical regions, white matter, caudate and putamen, ventricular system, and cerebellum. The mean volumes of these structures had variances in the range of 10-20%. The 34 brain volumes were transformed into the common coordinate system and then used to generate surface renderings with probabilistic threshold greater than 50%. This probabilistic threshold gave nearly quantitative recovery of the mean volumes in native space. The probabilistic volumes in stereotaxic space are now being used to extract time-radioactivity curves from dynamic PET recordings.

FDOPA metabolism in the adult porcine brain: influence of tracer circulation time and VOI selection on estimates of striatal DOPA decarboxylation

Different methodologies for PET data analysis influence the magnitude of estimates of blood-brain transfer coefficients and rate constants for the metabolism of FDOPA in living striatum. We now test the effects on several kinetic parameters of automatic procedures for volume of interest (VOI) selection. We also tested the sensitivity of the estimates to dynamic frame sequence duration, and produced a standard method for minimizing the variations in physiological estimates for FDOPA kinetics in minipig brain. We used minipigs because our previous work has shown them to provide an appropriate animal model for study normal and pathological cerebral DOPA metabolism using PET. Time-activity curves in striatum of adult minipigs were acquired in VOIs defined manually on MR-images, or alternatively on the basis of the radioactivity concentration based on the most radioactive voxel in the last scan frame. For all frame sequences, the relative decarboxylase activity (k(3)(D)) declined significantly (P < 0.006) as the VOI threshold declined from 95 to 70% of the most radioactive voxel. Irrespective of VOI size, the magnitude of k(3)(D) declined significantly (P < 0.001) from 0.074+/-0.008 to 0.045+/-0.005 per min (mean+/-S.E.M.) as total sequence length increased from 60 to 120 min circulation. The method of VOI selection had no significant effect on the striatum decarboxylation index of FDOPA calculated relative to the radioactivity in cerebellum (k(3)(S)).

The Danish PET/depression project: PET findings in patients with major depression

BACKGROUND

It is hypothesized from previous positron emission tomography (PET) studies of patients with major depression that dysfunction of regions of the limbic system and the frontal lobes in close connection with the basal ganglia is involved in the pathophysiology of major depression.

METHODS

By means of PET and 15O labelled radioactive water we determined an index of the neuronal activity by mapping the cerebral blood flow distribution of 42 unselected in-patients suffering from moderate to severe depression and 47 healthy controls controlling for age and gender. The PET maps were co-registered to magnetic resonance images of the anatomy of the brain.

RESULTS

The functions-of-interest analysis revealed significant gender differences in cerebral blood flow and changes in the relative distribution of the blood with increasing age. The patients had increased activity of the hippocampus and the cerebellum compared to the healthy controls when corrected for these confounders and the influence of antidepressant medication. Furthermore, data in the Danish Psychiatric Central Register showed that the patients studied were representative of the population of depressed patients admitted to the hospital during the study period.

CONCLUSION

Our main finding is increased blood flow to the hippocampus, even when controlling for a number of confounders. This is in accordance with a rapidly expanding literature suggesting an important role for this structure in major depression.

[Lack of doctors in rural districts--situation in Northern Norway, national challenge]

BACKGROUND

Recruitment of general practitioners to Northern Norway has failed during the last few years, especially in municipalities with a population of less than 4,000, though some small municipalities have maintained a stable medical service. What are the differences between municipalities with stable and unstable services?

MATERIAL AND METHODS

A questionnaire was mailed to the medical officers of the 89 municipalities in Northern Norway, with questions on the structure and organisation of the medical service, and factors influencing doctors' professional life and quality of life in general.

RESULTS

Answers from 62 municipalities were included. Municipalities with unstable services had longer distances to the nearest hospital, and doctors in these municipalities reported heavier work-load and professional isolation.

INTERPRETATION

A combination of factors concerning the structure and organisation of the primary health care seem to cause the increased difficulties in the unstable communities, hence they should have a potential for improvement.

Normalization of markers for dopamine innervation in striatum of MPTP-lesioned miniature pigs with intrastriatal grafts

As part of the DaNeX study, the uptake and binding of several positron emitting tracers was recorded in brain of healthy Göttingen minipigs, in minipigs with a syndrome of parkinsonism due to MPTP intoxication, and in parkinsonian minipigs which had received intrastriatal grafts of mesencephalic neurons from fetal pigs. The specific binding of [11C]NS 2214 to catecholamine uptake sites was reduced by two thirds in striatum of the intoxicated animals, while the rate constant for the decarboxylation of [18F]fluorodopa was reduced by 50% in the intoxicated animals. Several months after grafting, both pre-synaptic markers of dopamine fibres were normal in striatum. Dopamine depletion or grafting were without effect on the cerebral perfusion rate, measured with [15O]-water, did not alter the rate of oxygen metabolism (CMRO2) in brain, and did not alter the binding potential of tracers for dopamine D1 or D2 receptors in pig striatum. However, the grafting was associated with a local increase in the binding of [11C]PK 11195, a tracer for reactive gliosis, suggesting that an immunological reaction occurs at the site of graft, which might potentially have reduced the graft patency. However, this apparent immunological response did not preclude the re-establishment of normal [18F]fluorodopa and [11C]NS 2214 uptake in the allografted striatum.

The DaNeX study of embryonic mesencephalic, dopaminergic tissue grafted to a minipig model of Parkinson's disease: preliminary findings of effect of MPTP poisoning on striatal dopaminergic markers

A multicenter study is under way to investigate the efficacy of allografting of embryonic mesencephalic neurons in a pig model of Parkinson's disease. We have first established that a stable parkinsonian syndrome can be established by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication of adult male Göttingen minipigs. We are now using positron emission tomography (PET) methods for testing the physiological responses to MPTP intoxication and the time course of the response to several treatment strategies. We now report preliminary results obtained in 11 pigs employed in the initial phase of the study; the completed study shall ultimately include 30 pigs. Animals were randomly assigned to one of five groups: 1) Control, 2) MPTP intoxication, 3) MPTP intoxication followed by allograft, 4) MPTP intoxication followed by allograft with immunosuppression, and 5) MPTP intoxication followed by allograft with immunosuppression and co-grafting of immortalized HiB5 cells, which had been manipulated to secrete glia cell line-derived neurotrophic factor (GDNF) (approximately 2 ng GDNF/h/10(5) cells). MPTP was administered (1 mg/kg/day, SC) for 7-10 days until the pigs had developed mild parkinsonian symptoms of muscle rigidity, hypokinesia, and impaired coordination, especially of the hind limbs. Approximately 2 weeks after the last MPTP dose, animals received a T1-weighted magnetic resonance imaging (MRI) scan, and a series of dynamic PET recordings. After the first series of PET scans, four grafts of porcine embryonic mesencephalic tissue (E28 days) were placed in each striatum of some MPTP-intoxicated pigs, using MRI-based stereotactic techniques. Immunosuppression of some animals with cyclosporin and prednisolone began just prior to surgery. Two more series of PET scans were performed at 4-month intervals after surgery. After the last scans, pigs were killed and the brains were perfused for unbiased stereological examination of cytological and histochemical markers in striatum and substantial nigra. The behavioral impairment of the animals (the "Parkinson's score") had been evaluated throughout the 8-month period. Kinetic analysis of the first set of PET scans has indicated that the rate constant for the decarboxylation of FDOPA in catecholamine fibers was reduced by 33% in striatum of the mildly parkinsonian pigs. The rate of association of [11C]NS-2214 to catecholamine uptake sites was reduced by 62% in the same groups of pigs. No significant difference was found in the binding potential of [11C]raclopride to the dopamine D2-like receptors in striatum of the MPTP-intoxicated versus control pigs. These preliminary results are suggestive that the activity of DOPA decarboxylase may be upregulated in the partially denervated pig striatum.

Immediate allergic and nonallergic reactions to Christmas and Easter cacti

BACKGROUND

Occupational exposure to Christmas cacti has been reported as a cause of type I allergy. Therefore, the prevalence of immediate-type mucosal and skin reactions related to cactus exposure was studied in 103 employees in a cactus nursery.

METHODS

The study was based on a questionnaire followed by clinical examination, skin prick tests (SPT) with standard inhalant allergens and cacti, and a histamine-release test (HRT/Refix) using fresh cactus extracts as elicitor.

RESULTS

The questionnaire was answered by 84 (82%) of the nursery employees, and 63 (61%) were interviewed and skin prick tested; 58 of these were tested with HRT/Refix. Furthermore, 22 healthy controls were included and tested in vivo and in vitro. Cactus-related contact urticaria and/or rhinoconjunctivitis were reported by 37% of the cactus workers. Based on a combination of positive history, positive SPT, and positive HRT/ Refix to cactus, 8% of the cactus workers were allergic to cacti. No noncactus workers or controls were allergic to cacti by these criteria. Testing with fresh cactus material elicited positive SPT and negative HRT/Refix in 27 nursery workers and controls, of whom 12 had immediate-type skin and mucosal symptoms.

CONCLUSIONS

Christmas and Easter cacti seemed to be able to induce contact urticaria and rhinoconjunctivitis on both an immunologic and a nonimmunologic basis. Personal atopy was associated with positive reactions to cacti.

[Physicians in primary health care in Northern Norway 1995-97]

Recruiting general practitioners to Northern Norway is increasingly difficult. In 1997, 28% of all positions in primary health care in the counties of Nordland, Troms and Finnmark were vacant. Problems were worst in the small municipalities with a population of less than 4,000 with 37% of all positions vacant. The insufficient coverage of curative and acute health services is in part compensated for by a great number of short stay physicians. A cross-sectional study in the three northern countries in october 1998 showed that 68% of all general practitioners had Norwegian as their native language. In the small municipalities less than half the physicians were Norwegians.

PET neuroimaging with [11C]venlafaxine: serotonin uptake inhibition, biodistribution and binding in living pig brain

The brain binding kinetics and distribution of the antidepressant venlafaxine, labelled with 11C in the O-methyl position, was studied by PET after intravenous injection in anesthetized pigs. In addition, venlafaxine's action on serotonin (5-HT) uptake was studied in vitro in blood platelets obtain from humans or pigs. Venlafaxine resembled imipramine, paroxetine and citalopram in causing a dose-dependent inhibition of 5-HT uptake in blood platelets from pigs and humans. Venlafaxine-derived radioactivity entered the living brain readily and showed higher binding potentials in diencephalic and telencephalic regions than in cerebellum. Acute administration of an antidepressant drug (i.e. imipramine, citalopram or paroxetine) enhanced the distribution and altered the binding of venlafaxine in certain brain regions. The findings show that [11C]venlafaxine is not an ideal PET radiotracer mainly because of its relatively low binding potentials and its lack of specificity for the 5-HT transporter in living brain.

Distribution of bacterial populations in a stratified fjord (mariager fjord, denmark) quantified by in situ hybridization and related to chemical gradients in the water column

Volumn 62, no. 4, p. 1392, lines 37 and 38: "Aluminum oxide filters (0.2 mm pore size; Anopore; Millipore GmbH, Eschborn, Germany)" should read "Aluminum oxide filters (0.2 (mu)m pore size; Anopore; Whatman, Inc., Clifton, N.J.)." Page 1403, reference 15: "Fenchel, T." should read "Fenchel, T., L. D. Kristensen, and L. Rasmussen." [This corrects the article on p. 1391 in vol. 62.].

Distribution of bacterial populations in a stratified fjord (mariager fjord, denmark) quantified by in situ hybridization and related to chemical gradients in the water column

Volume 62, no. 4, p. 1391-1404: after publication of this article, it was brought to the attention of the authors that a more extensive treatment of the hydrodynamics of Mariager Fjord and the vertical distribution of bacteria and protozoa therein was published in a recent article by Fenchel et al. This work contains important information about the studied ecosystem, but unfortunately, the existence of this work was realized only after publication of our article. Thus, the following reference should have been cited in our article: [This corrects the article on p. 1391 in vol. 62.].

Distribution of bacterial populations in a stratified fjord (Mariager Fjord, Denmark) quantified by in situ hybridization and related to chemical gradients in the water column

The vertical distribution of major and intermediate electron acceptors and donors was measured in a shallow stratified fjord. Peaks of zero valence sulfur, Mn(IV), and Fe(III) were observed in the chemocline separating oxic surface waters from sulfidic and anoxic bottom waters. The vertical fluxes of electron acceptors and donors (principally O2 and H2S) balanced within 5%; however, the zones of oxygen reduction and sulfide oxidation were clearly separated. The pathway of electron transfer between O2 and H2S was not apparent from the distribution of sulfur, nitrogen, or metal compounds investigated. The chemical zonation was related to bacterial populations as detected by ethidium bromide (EtBr) staining and by in situ hybridization with fluorescent oligonucleotide probes of increasing specificity. About half of all EtBr-stained cells were detectable with a general oligonucleotide probe for all eubacteria when digital image analysis algorithms were used to improve sensitivity. Both EtBr staining and hybridization indicated a surprisingly uniform distribution of bacteria throughout the water column. However, the average cell size and staining intensity as well as the abundance of different morphotypes changed markedly within the chemocline. The constant overall cell counts thus concealed pronounced population shifts within the water column. Cells stained with a delta 385 probe (presumably sulfate-reducing bacteria) were detected at the chemocline at about 5 x 10(4) cells per ml, and this concentration increased to 2 x 10(5) cells per ml beneath the chemocline. A long slim rod-shaped bacterium was found in large numbers in the oxic part of the chemocline, whereas large ellipsoid cells dominated at greater depth. Application of selective probes for known genera of sulfate-reducing bacteria gave only low cell counts, and thus it was not possible to identify the dominant morphotypes of the sulfate-reducing community.

[Crib death and infant mortality in Scandinavia 1988-1993]

During the years 1970-1989 there was a marked increase in cot death in the Nordic countries Denmark, Finland, Norway and Sweden. Since 1990 cot death has decreased dramatically, especially in Norway and Denmark. Mortality rates have decreased by 74 per cent between 1989 and 1993 in Norway and by 69 per cent between 1991 and 1993 in Denmark. Investigations in Norway during the same period have shown a change in the sleeping positions of infants, from prone positions to supine/side positions. Infant mortality rates have decreased in all the Nordic countries and in 1993 varied from 5.45 per thousand live births in Denmark to 4.40 in Finland.

[Crib death and infant mortality in the Nordic countries 1988-93]

During the years 1970-89 there was a marked increase in cot deaths in the Nordic countries Denmark, Finland, Norway and Sweden. Since 1990 cot death has decreased dramatically, especially in Norway and Denmark. Mortality rates have decreased by 74% between 1989 and 1993 in Norway and by 69% between 1991 and 1993 in Denmark. Investigations in Norway during the same period have shown a change in the sleeping positions of infants, from prone positions to supine/side positions. Infant mortality rates have decreased in all the Nordic countries and in 1993 varied from 5.45 per thousand live births in Denmark to 4.40 in Finland.

[Change in infants' sleeping position and incidence of crib death in Northern Norway]

Several investigations have reported a prone sleeping position to be a risk factor for sudden infant death syndrome (SIDS). We investigated whether changes in sleeping position among infants in Northern Norway were associated with changes in SIDS rates. The prevalence of prone sleeping position was 54% among infants born in the years 1976-1989 and 5% among infants surveyed in May 1994. During the same period the SIDS rate declined from 2.75/1000 to 1.57/1000. These findings are consistent with other research in the field, and indicate that a prone sleeping position is a risk factor for SIDS.

Processes of care. Comparisons of certified nurse-midwives and obstetricians

Prenatal and intrapartum care provided to 1,181 women, all meeting risk requirements for nurse-midwifery care, by certified nurse-midwives (n = 471) and obstetricians (n = 710) are compared using indicators of physical and of educational/psychosocial components of maternity care. Data are from clinical records and questionnaires completed by the women. Bivariate analyses show that the two provider groups differ on some, but not all, processes of care. When the woman's evolving health status, personal characteristics, and preferences are controlled, there are significant differences that confirm two models of care. The nurse-midwifery approach emphasizes educational/psychosocial care and restrained, individualized use of technology. The obstetrics approach emphasizes more routine use of state-of-the-art technology. This study contributes new information to substantiate different models but also shows that both provider groups use elements of both. The difference in emphasis should encourage collaborative practice, given the shared basis for maternity care, whether it is provided by certified nurse-midwives or obstetricians.