Non-invasive analysis of metabolic reactions in body tissues,the case of myocardial fatty acids

1. In vivo observations of metabolic reactions require a) the knowledge of the metabolic pathway involved, b) the proper choice of tracer, c) the proper placement of tracer on to the substrate with respect to its anabolic and catabolic portion, d) counting techniques for separately observing the anabolic and catabolic substrate portion, e) proof of applicability of the method.
2. Fatty acid catabolism may be observed in the myocardium by choosing ¹²³I in the ω-position, thus altering heptadecanoic acid into a stearic acid analogue. This labelled fatty acid is accepted into the metabolic chain of reactions. The kinetics of uptake and release of this tracer, in mouse myocardium, are very similar to that of ¹¹C-labelled palmitic acid.
3. Because the ¹²³I labels both, the anabolic substrate as well as the final catabolites, which are released into the circulating blood and partially reenter the field of view, they must be separately measured in order to observe the release rate of anabolic tracer as a consequence of fatty acid degradation.
4. ¹²³I in the form of sodium iodide, was chosen to separately observe the catabolic tracer. The assumption is a diffusion rate constant similar for all types of catabolic tracer, i.e., iodinated small molecular acyl residues and free iodide. The catabolic tracer was substracted from the total tracer to yield the anabolically bound tracer.
5. The application of the correction procedure to separately observe the anabolic tracer in the myocardium combined with ECG-triggering of imaging in diastole, gives excellent myocardial scintigrams and permits the construction of metabolic images giving the rates of release of fatty acid labelling for each image segment of the myocardium. There is evidence that in coronary artery disease accumulation defects show a diminished release rate whereas in cardiomyopathy the accumulation image does not superimpose the metabolic image.
6. In order to utilize emission computer assisted tomography to its full potential one needs an acceptable speed of imaging for measuring elimination rates of tracer; also ECG triggering to any phase of a cardiac cycle should be applicable in order to improve the image quality; and finally repeated images from one or different tracers should be of interest in order to construct functional images giving metabolic reaction rates in term of elimination half times, besides the image of the initial tracer accumulation.

     

Prevalence of periodontitis in individuals with human leukocyte antigens (HLA) A9, B15, A2, and B5

Objective

Human leukocyte antigens (HLA) have been associated with periodontitis. Previous studies revealed HLA-A9 and HLA-B15 as potential susceptibility factors, while HLA-A2 and HLA-B5 might have protective effects. The aim of the study was to verify these associations in a group of HLA-typed blood donors with previously unknown periodontal status.

Materials and methods

In four German centers, 140 blood donors with known HLA class I status were enrolled and allocated to the following five groups: HLA-A9 (N = 24), HLA-B15 (N = 20), HLA-A2 (N = 30), HLA-B5 (N = 26), and controls (N = 40). Periodontal examination included the measurement of probing depths (PDs), clinical attachment level (CAL), bleeding on probing (BOP), and community periodontal index of treatment needs (CPITN).

Results

Carriers with HLA-A9 and HLA-B15 had higher values of mean PD (P < 0.0001), CAL (P < 0.0001), and BOP (P < 0.002) as well as sites with PD and CAL with ≥4 and ≥6 mm (P < 0.0003), respectively, than controls. Multiple regression analyses revealed HLA-A9, HLA-B15, and smoking as risk indicators for moderate to severe (CPITN 3–4; odds ratio (OR): 66.7, 15.3, and 5.1) and severe (CPITN 4; OR: 6.6, 7.4, and 3.8) periodontitis. HLA-A2 and HLA-B5 did not show any relevant associations.

Conclusion

The present data support a role of HLA-A9 and HLA-B15 as susceptibility factors for periodontitis, whereas HLA-A2 and HLA-B5 could not be confirmed as resistance factors.

Clinical relevance

Both HLA antigens A9 and B15 are potential candidates for periodontal risk assessment.

     

Dependency of the [18F]fluoromisonidazole uptake on oxygen delivery and tissue oxygenation in the porcine liver

We have previously shown that the accumulation of fluorine-18-labeled fluoromisonidazole ([¹⁸F]FMISO) is inversely correlated to tissue oxygenation, allowing the quantification of porcine liver tissue hypoxia in vivo. We determined the activity from administered [¹⁸F]FMISO in relation to the hepatic oxygen availability and the partial pressure of oxygen in tissue (tPO₂) to define a critical oxygen delivery on a regional basis. [¹⁸F]FMISO was injected 2 h after onset of regional liver hypoxia due to arterial occlusion of branches of the hepatic artery in 10 domestic pigs. During the experimental procedure the fractional concentration of inspired oxygen (FiO₂) was set to 0.67 in group A ( N=5) and to 0.21 in group B ( N=5) animals. Immediately before sacrifice, the tPO₂ was determined in normal flow and flow-impaired liver segments. The standardized uptake values (SUV) for [¹⁸F]FMISO was calculated from 659 single tissue samples obtained 3 h after injection of approximately 10 MBq/kg body weight [¹⁸F]FMISO and was compared with the regional total hepatic oxygen delivery (DO₂) calculated from the regional arterial and portal venous flow (based on ¹⁴¹Ce- and ^99mTc-microspheres measurements) and the oxygen content of the arterial and portal venous blood. In 121 tPO₂-measured liver tissue samples, the mean DO₂ was significantly decreased in occluded liver tissue samples [group A: 0.063 (0.044–0.089); group B: 0.046 (0.032–0.066)] compared to normal flow segments [group A: 0.177 (0.124–0.252); group B: 0.179 (0.128–0.25) mL·min⁻¹·g⁻¹; geometric mean (95% confidence limits); p < 0.01 in group A and p < 0.001 in group B]. The tPO₂ of occluded segments [group A: 5.1 (3.2–8.1); group B: 3.9 (2.4–6.2) mm Hg] was significantly decreased compared to normal flow segments [group A: 20.2 (12.6–32.5); group B: 22.4 (14.3–35.2) mm Hg; p < 0.01 in group A and p < 0.001 in group B]. Three hours after [¹⁸F]FMISO administration, the mean [¹⁸F]FMISO SUV determined in tPO₂-measured occluded segments was significantly higher [group A: 4.08 (3.12–5.34), group B: 5.43 (4.14–7.13)] compared to normal liver tissue [group A: 1.57 (1.2–2.06), group B: 1.5 (1.16–1.93); p < 0.001 for both groups]. The [¹⁸F]FMISO SUV allowed prediction of the tPO₂ with satisfying accuracy in hypoxic regions using the exponential regression curve { [¹⁸F]FMISO=1.05+6.7^{(−0.117 tPO₂}); r²=0.75;p < 0.001}. In addition, regardless of ventilation conditions, a significant exponential relationship between the DO₂ and the [¹⁸F]FMISO SUV was found ( r²=0.39,p < 0.001). Our results suggest that the reduction of the oxygen delivery below the critical range of 0.1–0.11 mL·min⁻¹·g⁻¹ regularly causes liver tissue hypoxia. The severity of hypoxia is reflected by the [¹⁸F]FMISO accumulation and allows the in vivo estimation of the tPO₂ in hypoxic regions.     

Genetic affinities among Mongol ethnic groups and their relationship to Turks

The central Asian country Mongolia is home to more than 20 tribes and ethnic groups, some of which are related to neighboring Turkic populations. The main Mongolian people, Khalkha, live in central and eastern Mongolia while the Tsaatan minority lives in the north of the country. The Oold minority is from the western Altai mountain region and live in close proximity with Turkic people. We have typed the HLA-A, -B, -Cw, -DRB1 and -DQB1 loci by PCR-SSP in these three Mongolian populations as well as a sample of the German population. To examine their genetic relationships, a sample of the Turkish population already typed at the HLA-A, -B and -DRB1 loci were used. Altogether five populations were analyzed: Khalkha (n = 100), Tsaatan (n = 72), Oold (n = 52), German (n = 260) and (Anatolian) Turkish (n = 498). Nei's unbiased genetic identity (GI) and genetic distance (GD) were estimated from genotypes using PopGene v1.31, and dendrograms were constructed using phylip. The results suggested a close relationship of the Khalkha to the Tsaatan. The Turks and Germans were equally distant to all three Mongolian populations. These results confirmed the lack of strong genetic relationship between the Mongols and the Turks despite the close relationship of their languages (Altaic group) and shared historical neighborhood. This study has provided useful population data for genetic and anthropologic studies bridging eastern and western populations.     

Meningioma: is there an association with human leukocyte antigens?

The expression of human leukocyte antigen (HLA) alleles plays an important role in the development and recurrence of benign and malignant diseases. Association of single HLA alleles or haplotypes with neoplastic processes has been investigated previously, and correlation between HLA and solid tumors, such as head and neck cancers or uterine cervical squamous epithelial lesions, were reported. However, there is no published data on the influence of the HLA system on the development of symptomatic cerebral meningioma, a mostly benign intracranial tumor of mesenchymal origin in adults. The present investigation is comparing the frequency of single HLA alleles and haplotypes in 81 adult Caucasian patients with symptomatic central nervous system meningiomas to that of 157 area- and race-matched healthy controls. Both standard serological and molecular genetic (PCR) techniques were used for HLA typing. Our results suggest an association between single HLA alleles and occurrence of clinically symptomatic meningioma. Patients with HLA-A*02 had a 2.5-fold increased risk of meningioma (P = 0.02), and those with HLA-DQB1*05 had a 1.8-fold increased risk of meningioma (P = 0.05). Conversely, HLA-A*01, -B*08, and -DRB1*03 were associated with a 0.4-, 0.5-, and 0.5-fold, respectively, decreased risk of meningioma (P = 0.008, P = 0.05, and P = 0.04). Moreover, the occurrence rate of combinations and estimated haplotypes containing these HLA alleles was strikingly different in meningioma patients compared with controls: significantly increased for the haplotypes HLA-A*02:DRB1*04 (P = 0.02, relative risk = 2.5) and HLA-A*02:DRB1*04:DQB1*0302,DQB1*05 (P = 0.03, RR = 7.5), and significantly decreased for the haplotype HLA-A*01:B*08:DRB1*03 (P = 0.01, relative risk = 0.2). In conclusion, these data suggest that some single HLA alleles and haplotypes may protect from or predispose to developing symptomatic central nervous system meningioma during adult life. These associations may be indicative of the involvement of the immune system in the host antitumor surveillance, recognition, and destruction of de novo arising human tumor cells.     

Influence of the major histocompatibility complex on age at onset of chronic lymphoid leukaemia

The major histocompatibility complex is one of the interactive factors in the multifactorial model of carcinogenesis. Its main influence in experimental models is on the age at onset of malignancies. We have previously shown a similar effect of homozygosity for HLA-DR53 in CML. In the present study, we investigated 79 patients with CLL and 329 local controls from Germany. In addition to full serotyping, all patients and 116 of controls were also typed by HLA-DRB PCR analysis. The homozygosity rates for DR53 in patients under and over the median age (60 years) were 18.6% and 2.9%, respectively (p = 0.03). Eight of the 9 homozygous patients were under the median age. The sex ratio in the DR53 homozygous group was reversed in favour of females. The homozygosity rates for DR53 were different in the overall groups of patients and controls, yielding a relative risk (RR) of 2.4 (p = 0.03). This association was stronger in the early-onset group compared to age-matched controls (RR = 4.4; p = 0.008) and for females with an early onset compared to age- and sex-matched controls (RR = 17.9; p = 0.0008). The simultaneous occurrence of the alleles of the haplotype A2B62DR4 showed a strong association with CLL (RR = 4.1; p = 0.002). This was probably the reason behind the association with HLA-DRB1*0401 (RR = 2.4; p = 0.009). Compared to the accelerating effect of HLA-DR53, HLA-DR52 showed a significant delaying effect on the onset of CLL. These findings confirmed the influence of the HLA complex on the development of another leukaemia. © 1996 Wiley-Liss, Inc.     

Introducing fluorine-18 fluoromisonidazole positron emission tomography for the localisation and quantification of pig liver hypoxia

Fluorine-18 labelled fluoromisonidazole ([¹⁸F]FMISO) has been shown to accumulate in hypoxic tissue in inverse proportion to tissue oxygenation. In order to evaluate the potential of [¹⁸F]FMISO as a possible positron emission tomography (PET) tracer for imaging of liver tissue hypoxia, we measured the [¹⁸F]FMISO uptake in 13 domestic pigs using dynamic PET scanning. Hypoxia was induced by segmental arterial hepatic occlusion. During the experimental procedure the fractional concentration of inspired oxygen (FiO₂) was set to 0.67 in group A (n=6) and to 0.21 in group B (n=7) animals. Before and after arterial occlusion, the partial pressure of O₂ in tissue (TPO₂) and the arterial blood flow were determined in normal flow and flow-impaired liver segments. Standardised uptake values [SUV=kBq tissue (in g) / body weight (in kg) × injected dose (in kBq)] for [¹⁸F]FMISO were calculated from PET images obtained 3 hours after injection of about 10 MBq/kg body weight [¹⁸F]FMISO. Immediately before PET scanning, the mean arterial blood flow was significantly decreased in arterially occluded segments [group A: 0.41 (0.32–0.52); group B: 0.24 (0.16–0.33) ml min^–1 g^–1] compared with normal flow segments [group A: 1.05 (0.76–1.46); group B: 1.14 (0.83–1.57) ml min^–1 g^–1; geometric mean (95% confidence limits); P<0.001 for both groups]. After PET scanning, the TPO₂ of occluded segments (group A: 5.1 (4.1–6.4); group B: 3.5 (2.6–4.9) mmHg] was significantly decreased compared with normal flow segments [group A: 26.4 (21.2–33.0); group B: 18.2 (13.3–25.1) mmHg; P<0.001 for both groups]. During the 3-h PET scan, the mean [¹⁸F]FMISO SUV determined in occluded segments increased significantly to 3.84 (3.12–4.72) in group A and 5.7 (4.71–6.9) in group B, while the SUV remained unchanged in corresponding normal liver tissue [group A: 1.4 (1.14–1.71); group B: 1.31 (1.09–1.57); P<0.001 for both groups]. Regardless of ventilation conditions, a significant inverse exponential relationship was found between the TPO₂ and the [¹⁸F]FMISO SUV (r ²=0.88, P<0.001). Our results suggest that because tracer delivery to hypoxic tissues was maintained by the portal circulation, the [¹⁸F]FMISO accumulation in the liver was found to be directly related to the severity of tissue hypoxia. Thus, [¹⁸F]FMISO PET allows in vivo quantification of pig liver hypoxia using simple SUV analysis as long as tracer delivery is not critically reduced. Received 27 July and in revised form 28 September 1998     

Nucleophilic [18F]Fluorination and subsequent decarbonylation of methoxy‐substituted nitro‐ and halogen‐benzenes activated by one or two formyl groups

As model reactions for the introduction of ¹⁸F into protected aromatic amino acids, the replacement of NO₂, Cl, Br and F by [¹⁸F]fluoride in 2‐isophthalaldehyde and 2‐terephthalaldehyde derivatives which model ¹⁸F‐DOPA and ¹⁸F‐tyrosine was investigated by comparing labelling yields and reaction rates with those of corresponding mono‐aldehyde compounds. All isophthalaldehydes showed maximum radiochemical yields (79 to 86%) at 140°C and in comparison with the corresponding mono‐aldehydes the reaction proceeded faster. At lower temperature the reaction already resulted in high yields, e.g. 2‐nitroisophthalaldehyde was labelled with a yield of 78% at 25°C after 7 min, whereas 2‐nitrobenzaldehyde only reached a yield of 1.7% under the same reaction conditions. The ¹⁸F/NO₂ exchange in nitroterephthalaldehydes proceeded more slowly and with lower radiochemical yields when compared with corresponding isophthalaldehydes and monoaldehydes. The decarbonylation of ¹⁸F‐labelled aromatic dialdehydic compounds with 4 eq. of Wilkinson's catalyst at 150°C in benzonitrile resulted in high yields, e.g. 2‐[¹⁸F]fluoro‐5‐methoxyisophthalaldehyde and 4‐[¹⁸F]fluoro‐2‐methoxy‐5‐methylisophthalaldehyde were decarbonylated efficiently with yields of 67±3% and 72±2%, respectively. Copyright © 2010 John Wiley & Sons, Ltd.     

Highly efficient automated synthesis of [C]choline for multi dose utilization

[¹¹C]Choline has been under investigation as a PET ligand for imaging tumor tissue, especially prostate cancer. An improved, automated synthesis of the tracer now was established. [¹¹C] Choline was produced by labeling 2-(dimethylamino)-ethanol (DMAE) with [¹¹C]CH₃I in a Tefzel^® tube at room temperature without solvent. The product was purified using a cation exchange cartridge. Reaction conditions were optimized with respect to synthesis time and amount of DMAE, resulting in radiochemical yields higher than 80% using 60 μl of DMAE in 20 min, radiochemical purity was >99% and residual DMAE was below 10 ppm. After ¹¹C-production of 1 h at 50 μA [¹¹C]choline activities of 30.0±5.6 GBq (n=29) were obtained in sterile solution ready for intravenous administration.     

Hypoxia-imaging with (18)F-Misonidazole and PET: changes of kinetics during radiotherapy of head-and-neck cancer.

BACKGROUND AND PURPOSE: PET with (18)F-Misonidazole (FMISO-PET) is a non-invasive method for measuring tumor hypoxia. We analysed changes of FMISO-uptake during radiotherapy and their impact on patient outcome. MATERIALS AND METHODS: Fourteen patients with HNC underwent repeated FMISO-PET prior to radiotherapy and after 30Gy. Dynamic and static PET-scans (2+4h p.i.) were acquired. FMISO-uptake was quantified by calculating standard uptake values (SUV) and tumor-muscle-ratios (TMR). Kinetic curve types representing tissue hypoxia were defined. Change of curve type was correlated with patient outcome. RESULTS: The mean SUV 4h p.i. and the TMR decreased significantly during radiotherapy. SUV decreased clearly in 12/14 patients, and increased in 2 patients. TMR decreased in 11 patients, and increased in 3 patients. Prior to radiotherapy, three different shapes of kinetic curve types indicative for the degree of hypoxia could be defined in 12/14 patients: (1) accumulation type (severe hypoxia (n=8)), (2) intermediate type (intermediate degree of hypoxia (n=3)), and (3) wash-out type (low degree of hypoxia (n=1)). Curve type changed towards a lower degree of hypoxia at 30Gy in all but 3 patients. In three patients curve type remained unchanged. CONCLUSIONS: The changes in tumor FMISO-uptake during radiotherapy indicate radio-induced reoxygenation.