Hippocampal Neurometabolite Changes in Hypothyroidism: An In Vivo (1) H Magnetic Resonance Spectroscopy Study Before and After Thyroxine Treatment

The hippocampus is a thyroid hormone receptor-rich region of the brain. A change in thyroid hormone levels may be responsible for an alteration in hippocampal-associated function, such as learning, memory and attention. Neuroimaging studies have shown functional and structural changes in the hippocampus as a result of hypothyroidism. However, the underlying process responsible for this dysfunction remains unclear. Therefore, the present study aimed to investigate the metabolic changes in the brain of adult hypothyroid patients during pre- and post-thyroxine treatment using in vivo proton magnetic resonance spectroscopy ((1) H MRS). (1) H MRS was performed in both healthy control subjects (n = 15) and hypothyroid patients (n = 15) (before and after thyroxine treatment). The relative ratios of the neurometabolites were calculated using the linear combination model (LCModel). Our results revealed a significant decrease of glutamate (Glu) (P = 0.045) and myo-inositol (mI) (P = 0.002) levels in the hippocampus of hypothyroid patients compared to controls. No significant changes in metabolite ratios were observed in the hypothyroid patients after thyroxine treatment. The findings of the present study reveal decreased Glu/tCr and mI/tCr ratios in the hippocampus of hypothyroid patients and these metabolite alterations persisted even after the patients became clinically euthyroid subsequent to thyroxine treatment.

Alterations of Functional Connectivity Among Resting-State Networks in Hypothyroidism

Hypothyroidism affects brain functioning as suggested by various neuroimaging studies. The primary focus of the present study was to examine whether hypothyroidism would impact connectivity among resting-state networks (RSNs) using resting-state functional magnetic resonance imaging (rsfMRI). Twenty-two patients with hypothyroidism and 22 healthy controls were recruited and scanned using rsfMRI. The data were analysed using independent component analysis and a dual regression approach that was applied on five RSNs that were identified using fsl software (http://fsl.fmrib.ox.ac.uk). Hypothyroid patients showed significantly decreased functional connectivity in the regions of the right frontoparietal network (frontal pole), the medial visual network (lateral occipital gyrus, precuneus cortex and cuneus) and the motor network (precentral gyrus, postcentral gyrus, precuneus cortex, paracingulate gyrus, cingulate gyrus and supramarginal gyrus) compared to healthy controls. The reduced functional connectivity in the right frontoparietal network, the medial visual network and the motor network suggests neurocognitive alterations in hypothyroid patients in the corresponding functions. However, the study would be further continued to investigate the effects of thyroxine treatment and correlation with neurocognitive scores. The findings of the present study provide further interesting insights into our understanding of the action of thyroid hormone on the adult human brain.

Diffusion tensor tractography in hypothyroidism and its correlation with memory function

Diffusion tensor tractography (DTT) was performed to determine the microstructural changes in the white matter fibre tracts of hypothyroid patients compared to controls and to correlate these changes with memory dysfunction scores. DTT and Postgraduate Institute Memory Scale test were performed in eight hypothyroid patients and eight healthy controls. Diffusion tensor imaging (DTI) measures [fractional anisotropy (FA) and mean diffusivity (MD)] from all of the major cerebral tracts were calculated and a comparison was made between the patient group and controls. Pearson's correlation was performed between Memory Dysfunction score and DTI measures. Significant changes in DTI measures were observed in various white matter fibre tracts in hypothyroid patients compared to controls. In hypothyroid patients, an inverse correlation of Memory Dysfunction score with FA was observed in the right and left inferior fronto-occipital fasciculus, whereas a positive correlation with MD was observed in the right anterior thalamic radiation among all white matter tracts. These findings suggest that microstructural changes in white matter fibres may contribute to the underlying dysfunction in memory in hypothyroid patients.

Voxel-based morphometric analysis in hypothyroidism using diffeomorphic anatomic registration via an exponentiated lie algebra algorithm approach

The present study aimed to investigate whether brain morphological differences exist between adult hypothyroid subjects and age-matched controls using voxel-based morphometry (VBM) with diffeomorphic anatomic registration via an exponentiated lie algebra algorithm (DARTEL) approach. High-resolution structural magnetic resonance images were taken in ten healthy controls and ten hypothyroid subjects. The analysis was conducted using statistical parametric mapping. The VBM study revealed a reduction in grey matter volume in the left postcentral gyrus and cerebellum of hypothyroid subjects compared to controls. A significant reduction in white matter volume was also found in the cerebellum, right inferior and middle frontal gyrus, right precentral gyrus, right inferior occipital gyrus and right temporal gyrus of hypothyroid patients compared to healthy controls. Moreover, no meaningful cluster for greater grey or white matter volume was obtained in hypothyroid subjects compared to controls. Our study is the first VBM study of hypothyroidism in an adult population and suggests that, compared to controls, this disorder is associated with differences in brain morphology in areas corresponding to known functional deficits in attention, language, motor speed, visuospatial processing and memory in hypothyroidism.

Magnetic resonance spectroscopy as a diagnostic modality for carcinoma thyroid

AIM

The aim of this study was to observe the findings of magnetic resonance spectroscopy of solitary thyroid nodules and its correlation with histopathology.

MATERIALS AND METHODS

In this study, magnetic resonance spectroscopy was carried out on 26 patients having solitary thyroid nodules. Magnetic resonance spectroscopy (MRS) was performed on a 1.5T super conductive system with gradient strength of 33mTs. Fine needle aspiration cytology was done after MRS. All 26 patients underwent surgery either because of cytopathologically proven malignancy or because of cosmetic reasons. Findings of magnetic resonance spectroscopy were compared with histopathology of thyroid specimens.

RESULTS AND CONCLUSION

It was seen that presence or absence of choline peak correlates very well with presence or absence of malignant foci with in the nodule (sensitivity=100%; specificity=88.88%). These results indicate that magnetic resonance spectroscopy may prove to be an useful diagnostic modality for carcinoma thyroid.

Differentiation of Malignant and Benign Solitary Thyroid Nodules Using 30- and 120-Minute Tc-99m MIBI Scans

Technetium-99m methoxy isobutylisonitrate (MIBI) has been found to be taken up by various tumors, including thyroid cancer. We prospectively evaluated 77 patients with cold thyroid solitary nodules on Tc-99m pertechnetate scintigraphy to evaluate the diagnostic value of Tc-99m MIBI scintigraphy. The aim of this study was to find out if thyroid nodules can be characterized on the basis of retention of MIBI and whether preoperative evaluation of malignancy is possible using this method. Single injection, dual-phase (30 and 120 minutes) thyroid scintigraphy using Tc-99m MIBI was performed in all these patients. In the following days and weeks, all patients underwent surgery. Using the 120/30-minute thyroid lesion to background radiouptake ratio (RUR), malignant and benign thyroid nodules could be separated with a sensitivity, specificity, and positive predictive value of 84.4%, 95.45%, and 93.33%, respectively. The mean RUR for malignant thyroid lesions was found to be 1.57+/-0.32, whereas for benign lesions, the ratio was significantly lower, 0.32+/-0.19. In conclusion, fine needle aspiration cytology along with the 120/30 minutes Tc-99m MIBI scintigraphy ratio appears to be useful in the preoperative assessment of solitary thyroid nodules.

Development and validation of hydroxy ethyl starch kits for instant use in gastroesophageal reflux and gastric motility studies

A reduction method based on stannous chloride is described to prepare hydroxy ethyl starch kits for gastrointestinal reflux and gastric motility studies. Following verification of the consistency of radiolabelling, in vitro experiments were carried out to validate 99mTc hydroxy ethyl starch as a liquid phase and solid phase gastric motility imaging radiotracer. Gastroesophageal reflux, liquid phase and solid phase studies were then conducted in 13 adult volunteers to examine the in vivo stability of the radiotracer. High labelling efficiency (>95% when prepared at neutral pH) was consistently achieved, which remained stable in conditions simulating gastric environment. Twelve of the 13 volunteers did not show absorption of any radioactivity from the gastro-intestinal tract. 99mTc hydroxy ethyl starch is a new agent suitable for gastroesophageal reflux and gastric motility studies. It is available in kit form and is a more 'physiological' agent than 99mTc sulphur colloid for preparing a solid radioactive meal. 99mTc hydroxy ethyl starch represents a true carbohydrate meal, and unlike 99mTc sulphur colloid, is easy to prepare and can easily be standardized to produce a standard vegetarian meal.

Local delivery of c-myc neutrally charged antisense oligonucleotides with transport catheter inhibits myointimal hyperplasia and positively affects vascular remodeling in the rabbit balloon injury model

Myointimal hyperplasia after percutaneous transluminal coronary angioplasty (PTCA) is a key component of the process of restenosis. The c-myc is a critical cell-cycle division protein involved in the formation of neointima. We evaluated the long-term impact of local delivery of c-myc neutrally charged antisense oligonucleotides (Resten-NG) on myointimal hyperplasia after PTCA in a rabbit model. PTCA was performed in the iliac arteries of 25 New Zealand white rabbits, using a Transport catheter at 8 atm for 30 sec, three times; 500 microg Resten-NG (n = 11) or saline (n = 14) was delivered to the PTCA site at 2 atm with the outer balloon for 2 min. The diet was supplemented with 0.25% cholesterol for 10 days before and 60 days after PTCA. Angiography was performed at harvest, and vessels were fixed in formalin, processed, and stained with hematoxylin and eosin (H&E) and Movat. Quantitative angiography showed that local delivery of antisense c-myc at PTCA reduced late luminal loss from 1.8 +/- 0.30 mm in control animals to 0.90 +/- 0.30 mm in the treatment group (P = 0.001). Histological analysis by planimetry showed that intimal areas were 1.67 +/- 0.44 mm(2) and 0.82 +/- 0.32 mm(2) in the control and antisense delivery groups, respectively (P < 0.05). We conclude that local delivery of Resten-NG inhibited myointimal hyperplasia after PTCA in cholesterol-fed rabbits for up to 60 days.

Low-power helium: neon laser irradiation enhances production of vascular endothelial growth factor and promotes growth of endothelial cells in vitro

BACKGROUND AND OBJECTIVE

Numerous reports suggest that low-power laser irradiation (LPLI) is capable of affecting cellular processes in the absence of significant thermal effect. The objective of the present study was to determine the effect of LPLI on secretion of vascular endothelial growth factor (VEGF) and proliferation of human endothelial cells (EC) in vitro.

STUDY DESIGN/MATERIALS AND METHODS

Cell cultures were irradiated with single different doses of LPLI (Laser irradiance from 0.10 to 6.3 J/cm(2)) by using a He:Ne continuous wave laser (632 nm). VEGF secretion by smooth muscle cells (SMC) and fibroblasts was quantified by sandwich enzyme immunoassay technique. The endothelial cell proliferation was measured by Alamar Blue assay. VEGF and transforming growth factor beta (TGF-beta) expression by cardiomyocytes was studied by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

We observed that (1) LPLI of vascular and cardiac cells results in a statistically significant increase of VEGF secretion in culture (1.6-fold for SMC and fibroblasts and 7-fold for cardiomyocytes) and is dose dependent (maximal effect was observed with LPLI irradiance of 0.5 J/cm(2) for SMC, 2.1 J/cm(2) for fibroblasts and 1.05 J/cm(2) for cardiomyocytes). (2) Significant stimulation of endothelial cell growth was obtained with LPLI-treated conditioned medium of SMC (maximal increase was observed with LPLI conditioned medium with irradiance of 1.05 J/cm(2) for SMC and 2.1 J/cm(2) for fibroblasts.

CONCLUSIONS

Our studies demonstrate that low-power laser irradiation increases production of VEGF by SMC, fibroblasts, and cardiac myocytes and stimulates EC growth in culture. These data may have significant importance leading to the establishment of new methods for endoluminal postangioplasty vascular repair and myocardial photoangiogenesis.

Perspectives on antisense therapy for the prevention of restenosis

One of the potential clinical applications of antisense therapy is the prevention or treatment of restenosis following coronary interventions. Inhibition of several cellular proto-oncogenes have been shown to inhibit smooth muscle cell proliferation in vitro and to reduce neointimal thickening in vivo. The clinical applicability of antisense technology, however, remains limited due to a relative lack of specificity, slow uptake across the cell membrane and rapid intracellular degradation of the oligonucleotide. The one study in humans with c-myc antisense yielded a negative result with respect to restenosis after stent implantation. Recent studies have introduced phosphorothioate morpholino oligomers (PMO), which represent an unusual DNA chemistry with a six-membered morpholino ring instead of a deoxyribose sugar. In addition, the charged phosphodiester internucleotide linkage is replaced by an uncharged phosphorothioate. The PMOs are resistant to serum nucleases found in serum and exhibit a high degree of specificity and efficacy in both in vitro and cell-free translation studies. In vivo studies in four different animal models of restenosis demonstrated significant reduction of myointimal response. The combination of enhanced efficacy and greater specificity introduced by the PMO chemistry led us to re-examine the potential efficacy of a neutrally charged c-myc antisense approach for the prevention of restenosis. Clinical studies are underway to investigate safety and efficacy of local delivery of this latest generation of antisense to reduce restenosis after coronary stenting.

Endoluminal reconstruction of the arterial wall with endothelial cell/glue matrix reduces restenosis in an atherosclerotic rabbit

OBJECTIVES

The objectives of this study were 1) to improve the attachment of reimplanted endothelial cells (EC) using a fibrin glue, and 2) to assess the impact of endothelial reseeding on restenosis eight weeks after balloon angioplasty.

BACKGROUND

A possible mechanism contributing to restenosis after balloon angioplasty is the loss of the EC lining. Previous attempts to reseed EC had little effect due to rapid loss of the seeded cells.

METHODS

Twelve atherosclerotic rabbits were subjected to angioplasty of iliac arteries and reseeding procedure. One iliac artery was subjected to EC/glue reconstruction and a contralateral site to EC seeding without glue. The animals were sacrificed after 4 h. In another series 12 rabbits were treated in the same fashion and were restudied at eight weeks. Additionally, in 10 animals one iliac was subjected to glue treatment, and another served as control.

RESULTS

Histological examination demonstrated the ability of this method to reattach the EC/glue matrix circumferentially to 68.0 +/- 6.7% of the arterial wall in comparison with 13.5 +/- 3.9% reattachment after EC seeding. Morphometry at eight weeks showed that the lumen area was significantly greater in the EC/glue group (1.23 +/- 0.35 mm2) than in the EC seeding alone (0.65 +/- 0.02 mm2) and 0.72 +/- 0.41 mm2 in the glue group. This was principally accounted for by the statistically significant differences in the intimal area (0.76 +/- 0.18 mm vs. 1.25 +/-0.26 mm2 and 1.01 +/- 0.53 mm2, respectively).

CONCLUSIONS

The attachment of EC after angioplasty can be greatly improved with fibrin glue matrix. The near 70% endothelial coverage achieved by this method resulted in a significant reduction of restenosis in atherosclerotic rabbit.

Angiogenesis in a patient with ischemic limb induced by intramuscular injection of vascular endothelial growth factor and fibrin platform

Direct revascularization of critical ischemia of the limb is often unsuccessful due to the anatomic extent and distribution of arterial occlusive disease, and no pharmacologic treatment has proved effective in treating this condition. Patients with ischemic limb may eventually require amputation and may develop serious morbidity and mortality. The goal of limb salvage in these patients has stimulated research into alternative treatment methods, including angiogenesis. Attempts have been made to apply growth factors directly or to encode DNA for such factors, but it is unknown whether these factors remain at the target site long enough to be effective. We report our strategy of using vascular endothelial growth factor in a fibrin network, which enables the sustained release of biologic material at the target site.

Augmentation of the expression of proangiogenic genes in cardiomyocytes with low dose laser irradiation in vitro

BACKGROUND AND OBJECTIVE

Several reports suggest that low power red laser light (LPRLL) is capable of affecting cellular processes in the absence of significant thermal effect. The objective of the present study was to determine the effect of LPRLL on proliferation of fetal cardiomyocytes in vitro and on the expression of proangiogenic genes, transforming growth factor-beta (TGF-beta), and vascular endothelial growth factor (VEGF).

STUDY DESIGN/MATERIALS AND METHODS

All cell cultures were irradiated with single-dose LPRLL using a He-Ne continuous wave laser (632 nm) with different doses. The effect of LPRLL on new DNA synthesis was studied by 3H thymidine-incorporation assay. VEGF and TGF-beta expression by cardiomyocytes was studied by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

We observed that a dose-dependent increase in cardiomyocytes proliferation can be obtained with LPRLL and that there is a significant increase in VEGF and TGF-beta mRNA expression by cardiomyocytes.

CONCLUSIONS

These data may have significant importance leading to the establishment of new methods for myocardial photoangiogenesis and photoregeneration as well as in vitro proliferation of cardiac myocytes.

Role of radionuclide perfusion study in cold solitary thyroid nodule for diagnosis of malignancy: a complimentary diagnostic modality to fine needle aspiration cytology

One hundred and forty eight subjects with euthyroid solitary thyroid nodules (STN) were taken up for radionuclide perfusion study. They were found to have a cold STN on 99mTc thyroid static scan. All had fine needle aspiration cytology (FNAC), and except for subjects with chronic lymphocytic thyroiditis, were subjected to surgery for tissue diagnosis by histopathology. The diagnostic findings in these patients of solitary thyroid nodules were correlated with the histopathology. Radionuclide perfusion study is considered useful to differentiate benign from malignant cold thyroid solitary nodules with high degree of sensitivity (95%) and specificity (87.9%).

Predictor of outcome of hyperthyroidism due to Graves disease: serum triiodothyronine/thyroxine ratio

There is a proportionally greater increase in the serum T3 than Serum T4 concentration in patients with hyperthyroidism due to Grave's disease which results in an elevation of serum T3 to T4 ratio. The study was undertaken to investigate the alteration of serum T3 to T4 ratio in relation to the outcome of antithyroid drug therapy. 98 patients of hyperthyroid Grave's disease were studied and 78 patients had T3 to T4 ratio greater than 20 ng/microgram before therapy (normal range 14-20; mean 16.0) In 16 out of 78 patient T3 to T4 ratio remained high during a 18 months course of antithyroid drug therapy and in 13 of them (81%) hyperthyroidism recurred after stoppage of treatment. In the remaining 62 patients, the initial high T3 to T4 ratio became normal (< 20) during treatment and 34 of them (54.9%) had a remission of the disease after stoppage of the drug. Of the 20 patients in whom the initial T3 to T4 ratios were within normal range, the ratio remained normal during treatment and 16(80%) had a remission. Goiter size was larger in patients with high serum T3 to T4 ratio and reduction of goiter size occurred in some patients (59%) with decreasing T3 to T4 ratios. It is concluded that serum T3 to T4 ratio is a single and a useful predictor of the outcome of antithyroid drug therapy in patients with hyperthyroidism due to Grave's disease. A ratio greater than 20 throughout therapy indicates that the chances of relapse is high and a ratio below 20 either initially or during therapy is an indication of prolonged remission.

Scintigraphic diagnosis of protein losing enteropathy using Tc-99m dextran

The authors performed abdominal scintigraphy using intravenously administered Tc-99m dextran in a patient with protein losing enteropathy. The study revealed abnormal leakage of the radiotracer in the left lumber area that moved over time in a pattern suggestive of small intestinal transit. Besides being a nonprotein and having long stay in intravascular compartment, the macromolecule may have many advantages over Tc-99m human serum albumin, the current radiotracer of choice for imaging intestinal protein loss.

99Tcm-dextran: a potential inflammation-seeking radiopharmaceutical

The aim of this study was to test whether 99Tcm-dextran can be used for imaging inflammation. An in vivo inflammation model was prepared by intramuscular (i.m.) injection of Freund's complete adjuvant to the thigh of five rabbits. Serial imaging of the animals was done with 99Tcm-dextran for 2 weeks following the onset of inflammation. The radiotracer was seen to concentrate selectively in the lesion, with a mean target-to-nontarget ratio of 3.01 (range 2.74-3.15) from day 4 onwards. The area of scintiscan abnormality increased with time and was more marked than the physical appearance of the lesion. In two rabbits, the tracer was also seen to localize at the site of injection of the anaesthesia in the normal thigh. The best time to image was found to be 2-4 h after 99Tcm-dextran administration. It would appear that abnormally increased capillary permeability in the inflamed area results in enhanced uptake of the macromolecule. We conclude that 99Tcm-dextran is a potential inflammation-seeking radiotracer, though it needs to be evaluated further.

Radionuclide angiography in evaluation of cold solitary thyroid nodules. Improved diagnostic accuracy using flow and washout analysis

Radionuclide thyroid angiography was performed in 252 patients with hypofunctioning thyroid nodules to evaluate differences in vascular flow and washout patterns in benign and malignant disease. Time activity curves of Tc-99m pertechnetate flow through the cold nodules were generated using region of interest software. Retention ratios of counts in the nodule at 2 minutes after radionuclide administration versus those at peak activity were derived. Patients subsequently underwent surgical excision and histopathologic examination. One hundred forty-four of the 204 benign nodules were avascular with absent radionuclide flow through the nodule. Fifty-six benign nodules were vascular with a prolonged radionuclide washout pattern with retention ratios ranging from 0.62-0.92. Forty-six of the 48 malignant nodules displayed increased perfusion with rapid radionuclide washout with retention ratios ranging from 0.28-0.48. Four benign nodules exhibited a similar flow and washout pattern. Radionuclide thyroid angiography with vascular flow and washout analysis appears to be a useful technique to differentiate between benign and malignant thyroid nodules with a high degree of sensitivity and specificity.