Biochemical markers of fatal hypothermia.

The aim of this study was to investigate the usefulness of postmortem biochemical investigations in the diagnosis of fatal hypothermia. 10 cases of fatal hypothermia and 30 control cases were selected. A series of biochemical parameters, such as glucose, acetone, 3-beta-hydroxybutyrate, isopropyl alcohol, free fatty acids, adrenaline, growth hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, cortisol, calcium, magnesium, C-reactive protein, procalcitonin as well as markers of renal and cardiac functions were measured in blood, postmortem serum from femoral blood, urine, vitreous and pericardial fluid. The results suggested that deaths due to hypothermia, especially in free-ethanol cases, are characterized by increased ketone levels in blood and other biological fluids, increased adrenaline concentrations in urine, increased cortisol levels in postmortem serum from femoral blood and increased free cortisol values in urine. Increased or decreased levels of other biological parameters are either the result of terminal metabolic changes or the expression of preexisting diseases and may provide information to elucidate the death process on a case-by-case basis.

Unilateral cricothyroid contraction and glottic configuration.

It is frequently stated that unilateral cricothyroid muscle (CT) paralysis can be diagnosed by physical examination, noting rotation of the glottis, and shortening and vertical displacement of the ipsilateral vocal fold. These signs, however, are inconsistently observed, and there is considerable controversy regarding the direction of glottic rotation. To determine the effects of CT contraction on three-dimensional glottic configuration, we performed computerized tomography on cadaver larynges before and after simulated CT contraction. Radiopaque makers were used to compute distances. Unilateral CT contraction equally increased the length of both membranous vocal folds, and rotated the posterior glottis less than 1 mm. CT contraction neither adducted the vocal processes, nor significantly their altered vertical level. These results suggest that unilateral CT paralysis cannot be diagnosed on the basis of any clinically apparent change in glottal configuration.

Traitement chirurgical de la diplopie secondaire à l'orbitopathie dysthyroïdienne [Surgical treatment of diplopia in Graves' orbitopathy]

BACKGROUND: The correction of oculomotor disorder in Grave's disease is applied on pathological extraocular muscles. Based on the global muscular restriction (bilateral forced duction test) and angular measurements, we have used a non-adjustable technique. PATIENTS AND METHODS: We performed a retrospective analysis of 21 patients (23 operations) with thyroid-associated orbitopathy operated for persisting diplopia. The angles of deviation in the 9 diagnostic directions of gaze and the field of binocular vision were measured with the Harm's tangent scale before and after surgery. Sixteen patients were operated only on vertical muscles. The mean follow-up was 45 months. RESULTS: 76 % of the patients (95 % confidence interval [CI], 58-94 %) obtained a large and centred field of binocular vision without prisms. 14 % (95 % CI, 0-29 %) had binocular vision with the use of prisms. Diplopia persisted in one patient despite 3 operations. Taking into consideration the interventions done before the patient was referred to us, the reintervention rate was 13 % (95 % CI, 0-28 %). CONCLUSIONS: A binocular field of vision can be successfully restored in the majority of patients with Graves' orbitopathy, using a non-adjustable surgical technique.

Lethal skeletal dysplasia in mice and humans lacking the golgin GMAP-210.

BACKGROUND: Establishing the genetic basis of phenotypes such as skeletal dysplasia in model organisms can provide insights into biologic processes and their role in human disease. METHODS: We screened mutagenized mice and observed a neonatal lethal skeletal dysplasia with an autosomal recessive pattern of inheritance. Through genetic mapping and positional cloning, we identified the causative mutation. RESULTS: Affected mice had a nonsense mutation in the thyroid hormone receptor interactor 11 gene (Trip11), which encodes the Golgi microtubule-associated protein 210 (GMAP-210); the affected mice lacked this protein. Golgi architecture was disturbed in multiple tissues, including cartilage. Skeletal development was severely impaired, with chondrocytes showing swelling and stress in the endoplasmic reticulum, abnormal cellular differentiation, and increased cell death. Golgi-mediated glycosylation events were altered in fibroblasts and chondrocytes lacking GMAP-210, and these chondrocytes had intracellular accumulation of perlecan, an extracellular matrix protein, but not of type II collagen or aggrecan, two other extracellular matrix proteins. The similarities between the skeletal and cellular phenotypes in these mice and those in patients with achondrogenesis type 1A, a neonatal lethal form of skeletal dysplasia in humans, suggested that achondrogenesis type 1A may be caused by GMAP-210 deficiency. Sequence analysis revealed loss-of-function mutations in the 10 unrelated patients with achondrogenesis type 1A whom we studied. CONCLUSIONS: GMAP-210 is required for the efficient glycosylation and cellular transport of multiple proteins. The identification of a mutation affecting GMAP-210 in mice, and then in humans, as the cause of a lethal skeletal dysplasia underscores the value of screening for abnormal phenotypes in model organisms and identifying the causative mutations.

Control of the peroxisomal beta-oxidation pathway by a novel family of nuclear hormone receptors.

Three novel members of the Xenopus nuclear hormone receptor superfamily have been cloned. They are related to each other and similar to the group of receptors that includes those for thyroid hormones, retinoids, and vitamin D3. Their transcriptional activity is regulated by agents causing peroxisome proliferation and carcinogenesis in rodent liver. All three Xenopus receptors activate the promoter of the acyl coenzyme A oxidase gene, which encodes the key enzyme of peroxisomal fatty acid beta-oxidation, via a cognate response element that has been identified. Therefore, peroxisome proliferators may exert their hypolipidemic effects through these receptors, which stimulate the peroxisomal degradation of fatty acids. Finally, the multiplicity of these receptors suggests the existence of hitherto unknown cellular signaling pathways for xenobiotics and putative endogenous ligands.

Comparison of the metabolic and endocrine effects of 3,5,3'-triiodothyroacetic acid and thyroxine.

To test the hypothesis that 3,5,3'-triiodothyroacetic acid (Triac) is more active as a TSH suppressor than on peripheral parameters of thyroid hormone action, the following parameters were studied: basal metabolic rate, sleeping energy expenditure (SEE), sex hormone-binding globulin, and cholesterol. In a double blind trial, 14 subjects received during 3 weeks (phase 1) 180 micrograms T4 or 1700 micrograms Triac daily, divided into 3 doses, to suppress thyroidal secretion. The dosage was doubled for the next 3 weeks (phase 2). Under T4 treatment, TSH reached 0.11 mU/L during phase 1 and less than 0.03 mU/L during phase 2. With Triac, a marked TSH inhibition occurred after 1 week (0.17 mU/L), followed by an escape during the following 2 weeks (0.63 mU/L). During phase 2, an almost complete TSH suppression was obtained (0.03 mU/L). Both Triac doses suppressed endogenous thyroid hormone secretion, as evidenced by T4 and rT3 levels. Both substances induced a 2-fold stimulation of sex hormone-binding globulin during phase 2. Serum cholesterol decreased similarly, without affecting the high/low density lipoprotein ratio. T4 increased SEE by 4.1% and 8.5% during phases 1 and 2. Triac failed to induce the expected peripheral metabolic responses of the thyroid hormones, as demonstrated by an unchanged SEE and basal metabolic rate. These results clearly show a preferential action of Triac on TSH suppression.

Influence of sex and age on T3 receptors and T3 concentration in the pituitary gland of the rat: consequences on TSH secretion.

A reduced secretion of thyroid hormones with age has been documented in humans and animals with no substantial increase in TSH secretion, which may be indicative of an age-related impairment of the pituitary sensitivity to the negative control exerted by thyroid hormones. We have evaluated in rats the influence of sex and age on pituitary T3 nuclear receptors--known to be determinant in the regulation of TSH secretion--as well as on T3 concentration in the pituitary gland. As regards sex, the density of T3 receptors and the concentration of T3 in pituitary gland and plasma were greater in females than in males whereas pituitary and plasma TSH concentrations were less. As for age, the density of T3 receptors was greater in old male rats than in young ones with no changes in pituitary T3 and plasma TSH concentrations. In old female rats in contrast, there was no significant increase in T3 receptors but pituitary T3 was less and plasma TSH greater than in young female rats. In both sexes plasma thyroid hormones and pituitary TSH were reduced with age whereas TSH response to TRH was not altered. These results illustrate sex and age differences in pituitary T3 receptors and pituitary T3 concentration as well as in TSH secretion. In young animals of both sexes an inverse correlation is observed between the density of pituitary T3 receptors and plasma TSH. In contrast, in old animals the absence of this correlation is suggestive of an age-related impairment of T3 action on the thyrotrophs or of changes pertaining to other factors modulating TSH secretion.

Effect of hypoxia on cerebral blood flow regulation during rest and exercise : role of cerebral oxygen delivery on performance

Adequate supply of oxygen to the brain is critical for maintaining normal brain function. Severe hypoxia, such as that experienced during high altitude ascent, presents a unique challenge to brain oxygen (O2) supply. During high-intensity exercise, hyperventilation-induced hypocapnia leads to cerebral vasoconstriction, followed by reductions in cerebral blood flow (CBF), oxygen delivery (DO2), and tissue oxygenation. This reduced O2 supply to the brain could potentially account for the reduced performance typically observed during exercise in severe hypoxic conditions. The aims of this thesis were to document the effect of acute and chronic exposure to hypoxia on CBF control, and to determine the role of cerebral DO2 and tissue oxygenation in limiting performance during exercise in severe hypoxia. We assessed CBF, arterial O2 content (CaO2), haemoglobin concentration ([Hb]), partial pressure of arterial O2 (PaO2), cerebrovascular CO2 reactivity, ventilatory response to CO2, cerebral autoregulation (CA), and estimated cerebral DO2 (CBF ⨉ CaO2) at sea level (SL), upon ascent to 5,260 m (ALT1), and following 16 days of acclimatisation to 5,260 m (ALT16). We found an increase in CBF despite an elevated cerebrovascular CO2 reactivity at ALT1, which coincided with a reduced CA. Meanwhile, PaO2 was greatly decreased despite increased ventilatory drive at ALT1, resulting in a concomitant decrease in CaO2. At ALT16, CBF decreased towards SL values, while cerebrovascular CO2 reactivity and ventilatory drive were further elevated. Acclimatisation increased PaO2, [Hb], and therefore CaO2 at ALT16, but these changes did not improve CA compared to ALT1. No differences were observed in cerebral DO2 across SL, ALT1, and ALT16. Our findings demonstrate that cerebral DO2 is maintained during both acute and chronic exposure to 5,260 m, due to the reciprocal changes in CBF and CaO2. We measured middle cerebral artery velocity (MCAv: index of CBF), cerebral DO2, ventilation (VE), and performance during incremental cycling to exhaustion and 15km time trial cycling in both normoxia and severe hypoxia (11% O2, normobaric), with and without added CO2 to the inspirate (CO2 breathing). We found MCAv was higher during exercise in severe hypoxia compared in normoxia, while cerebral tissue oxygenation and DO2 were reduced. CO2 breathing was effective in preventing the development of hyperventilation-induced hypocapnia during intense exercise in both normoxia and hypoxia. As a result, we were able to increase both MCAv and cerebral DO2 during exercise in hypoxia with our CO2 breathing setup. However, we concomitantly increased VE and PaO2 (and presumably respiratory work) due to the increased hypercapnic stimuli with CO2 breathing, which subsequently contributed to the cerebral DO2 increase during hypoxic exercise. While we effectively restored cerebral DO2 during exercise in hypoxia to normoxic values with CO2 breathing, we did not observe any improvement in cerebral tissue oxygenation or exercise performance. Accordingly, our findings do not support the role of reduced cerebral DO2 in limiting exercise performance in severe hypoxia. -- Un apport adéquat en oxygène au niveau du cerveau est primordial pour le maintien des fonctions cérébrales normales. L'hypoxie sévère, telle qu'expérimentée au cours d'ascensions en haute altitude, présente un défi unique pour l'apport cérébral en oxygène (O2). Lors d'exercices à haute intensité, l'hypocapnie induite par l'hyperventilation entraîne une vasoconstriction cérébrale suivie par une réduction du flux sanguin cérébral (CBF), de l'apport en oxygène (DO2), ainsi que de l'oxygénation tissulaire. Cette réduction de l'apport en O2 au cerveau pourrait potentiellement être responsable de la diminution de performance observée au cours d'exercices en condition d'hypoxie sévère. Les buts de cette thèse étaient de documenter l'effet de l'exposition aiguë et chronique à l'hypoxie sur le contrôle du CBF, ainsi que de déterminer le rôle du DO2 cérébral et de l'oxygénation tissulaire comme facteurs limitant la performance lors d'exercices en hypoxie sévère. Nous avons mesuré CBF, le contenu artériel en oxygène (CaO2), la concentration en hémoglobine ([Hb]), la pression partielle artérielle en O2 (PaO2), la réactivité cérébrovasculaire au CO2, la réponse ventilatoire au CO2, et l'autorégulation cérébrale sanguine (CA), et estimé DO2 cérébral (CBF x CaO2), au niveau de la mer (SL), au premier jour à 5.260 m (ALT1) et après seize jours d'acclimatation à 5.260 m (ALT16). Nous avons trouvé des augmentations du CBF et de la réactivité cérébrovasculaire au CO2 après une ascension à 5.260 m. Ces augmentations coïncidaient avec une réduction de l'autorégulation cérébrale. Simultanément, la PaO2 était grandement réduite, malgré l'augmentation de la ventilation (VE), résultant en une diminution de la CaO2. Après seize jours d'acclimatation à 5.260 m, le CBF revenait autour des valeurs observées au niveau de la mer, alors que la réactivité cérébrovasculaire au CO2 et la VE augmentaient par rapport à ALT1. L'acclimatation augmentait la PaO2, la concentration en hémoglobine, et donc la CaO2, mais n'améliorait pas l'autorégulation cérébrale, comparé à ALT1. Aucune différence n'était observée au niveau du DO2 cérébral entre SL, ALT1 et ALT16. Nos résultats montrent que le DO2 cérébral est maintenu constant lors d'expositions aiguë et chronique à 5.260m, ce qui s'explique par la réciprocité des variations du CBF et de la CaO2. Nous avons mesuré la vitesse d'écoulement du sang dans l'artère cérébrale moyenne (MCAv : un indice du CBF), le DO2 cérébral, la VE et la performance lors d'exercice incrémentaux jusqu'à épuisement sur cycloergomètre, ainsi que des contre-la-montres de 15 km en normoxie et en hypoxie sévère (11% O2, normobarique) ; avec ajout ou non de CO2 dans le mélange gazeux inspiré. Nous avons trouvé que MCAv était plus haute pendant l'exercice hypoxique, comparé à la normoxie alors que le DO2 cérébral était réduit. L'ajout de CO2 dans le gaz inspiré était efficace pour prévenir l'hypocapnie induite par l'hyperventilation, qui se développe à l'exercice intense, à la fois en normoxie et en hypoxie. Nous avons pu augmenter MCAv et le DO2 cérébral pendant l'exercice hypoxique, grâce à l'ajout de CO2. Cependant, nous avons augmenté la VE et la PaO2 (et probablement le travail respiratoire) à cause de l'augmentation du stimulus hypercapnique. Alors que nous avons, grâce à l'ajout de CO2, efficacement restauré le DO2 cérébral au cours de l'exercice en hypoxie à des valeurs obtenues en normoxie, nous n'avons observé aucune amélioration dans l'oxygénation du tissu cérébral ou de la performance. En conséquence, nos résultats ne soutiennent pas le rôle d'un DO2 cérébral réduit comme facteur limitant de la performance en hypoxie sévère.

Effects of lactate on glucose metabolism in healthy subjects and in severely injured hyperglycemic patients.

Hepatic glucose production is autoregulated during infusion of gluconeogenic precursors. In hyperglycemic patients with multiple trauma, hepatic glucose production and gluconeogenesis are increased, suggesting that autoregulation of hepatic glucose production may be defective. To better understand the mechanisms of autoregulation and its possible alterations in metabolic stress, lactate was coinfused with glucose in healthy volunteers and in hyperglycemic patients with multiple trauma or critical illness. In healthy volunteers, infusion of glucose alone nearly abolished endogenous glucose production. Lactate increased gluconeogenesis (as indicated by a decrease in net carbohydrate oxidation with no change in total [13C]carbohydrate oxidation) but did not increase endogenous glucose production. In patients with metabolic stress, endogenous glucose production was not suppressed by exogenous glucose, but lactate did not further increase hepatic glucose production. It is concluded that 1) in healthy humans, autoregulation of hepatic glucose production during infusion of lactate is still present when glycogenolysis is suppressed by exogenous glucose and 2) autoregulation of hepatic glucose production is not abolished in hyperglycemic patients with metabolic stress.

Transcranial Doppler after traumatic brain injury: is there a role?

PURPOSE OF REVIEW: To present the practical aspects of transcranial Doppler (TCD) and provide evidence supporting its use for the management of traumatic brain injury (TBI) patients. RECENT FINDINGS: TCD measures systolic, mean, and diastolic cerebral blood flow (CBF) velocities and calculates the pulsatility index from basal intracranial arteries. These variables reflect the brain circulation, provided there is control of potential confounding factors. TCD can be useful in patients with severe TBI to detect low CBF, for example, during intracranial hypertension, and to assess cerebral autoregulation. In the emergency room, TCD might complement brain computed tomography (CT) scan and clinical examination to screen patients at risk for further neurological deterioration after mild-to-moderate TBI. SUMMARY: The diagnostic value of TCD should be incorporated into other findings from multimodal brain monitoring and CT scan to optimize the bedside management of patients with TBI and help guide the choice of appropriate therapies.

Biokinetics and dosimetry of 111 In-DOTA-NOC-ATE compared with 111In-DTPA-Octreotide

Aim: Biokinetics and dosimetry of 111In-DOTA-NOC-ATE (NOCATE) and 111In-DTPA-octreotide (Octreoscan?, OCTREO) were comparatively studied in the same patients. Patients and Methods: Seventeen patients (10 males, 7 females), mean age 60 years referred for an Octreoscan? because of carcinoid (N=9), unspecified neurodendocrine tumors (N=6), thymoma (N=1) or medullary thyroid carcinoma (N=1) accepted a second study with NOCATE. Four patients had no detectable tumor at the time of scanning. Whole-body (WB) anterior-posterior scans were recorded 0.5 (100% reference scan), 4, 24 and 48 hrs (N=17) and 120 hrs (N=6) after injection. OCTREO (178±15 MBq) preceded NOCATE (108±14 MBq) imaging with 16±5 days in 16 patients while 1 patient had first NOCATE followed 14 days later by OCTREO. Blood samples were taken 5, 15, 30, 60, 240 and 1440 min after injection. Background corrected geometric mean counts of WB, lung, kidney, liver, spleen and blood counts expressed in % of the initial composite WB and blood counts, respectively were fitted to bi- or single exponential curves and dosimetry was performed for male and female patients using MIRDOSE3.1 and OLINDA/EXM. Results: Initially, WB, lung and kidney activity was similar but retention was significantly higher for NOCATE compared with OCTREO. Liver and spleen uptake of NOCATE was higher from beginning (p<0.001) and remained so over time. Activity in rest of body showed similar α and β half-lives, but the β half-life fraction of NOCATE was much higher than OCTREO (49% vs. 19%, respectively). Blood T1/2β was longer for NOCATE compared with OCTREO (19 vs. 6h). Residence times were similar in male and female patients while they were in both genders higher for NOCATE than OCTREO. Consequently, effective dose (ED) for NOCATE (ED 114 and 134 μSv/MBq for man and women, respectively) exceeded that of OCTREO (ED = 61 and 71 μSv/MBq), the latter results being close to the ICRP-published radiation dose of OCTREO (ED = 54 and 71 µSv/MBq, respectively). Differential activity measurement in blood cells and plasma showed that only a minor fraction of NOCATE and OCTREO (<5 % in the mean) was bound to globular blood components. Conclusions: NOCATE showed higher retention in normal organs and delivered roughly twice the radiation dose of OCTREO. The ED of OCTREO in these patients was similar to ICRP80 report when adopting a bladder voiding interval of 2 hours.

Peroxisome proliferator-activated receptors A link between endocrinology and nutrition?

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily like the steroid, thyroid, or retinoid hormone receptors, which are ligand-activated transcription factors regulating gene expression. PPARs mediate the induction of the enzymes of the peroxisomal and microsomal fatty-acid oxidation pathways by hypolipidemic drugs such as clofibrate and are probably also involved in the gene expression of other lipid-metabolism-associated proteins that are controlled by fibrate hypolipidemic drugs. That PPARs play an important role in the regulation of lipid metabolism is reinforced by the discovery of their activation by physiologic concentrations of fatty acids. This observation raises the question of whether fatty acids are ligands of PPARs, which would imply that nutritional fatty acids can act like hormones.

Effects of thyromimetic drugs on aldosterone-dependent sodium transport in the toad bladder.

Aldosterone increases transepithelial Na+ transport in the urinary bladder of Bufo marinus. The response is characterized by 3 distinct phases: 1) a lag period of about 60 min, ii) an initial phase (early response) of about 2 hr during which Na+ transport increases rapidly and transepithelial electrical resistance falls, and iii) a late phase (late response) of about 4 to 6 hr during which Na+ transport still increases significantly but with very little change in resistance. Triiodothyronine (T3, 6 nM) added either 2 or 18 hr before aldosterone selectively antagonizes the late response. T3 per se (up to 6 nM) has no effect on base-line Na+ transport. The antagonist activity of T3 is only apparent after a latent period of about 6 to 8 hr. It is not rapidly reversible after a 4-hr washout of the hormone. The effects appear to be selective for thyromimetic drugs since reverse T3 (rT3) is inactive and isopropyldiiodothyronine (isoT2) is more active than T3. The relative activity of these analogs corresponds to their relative affinity for T3 nuclear binding sites which we have previously described. Our data suggest that T3 might control the expression of aldosterone by regulating gene expression, e.g. by the induction of specific proteins, which in turn will inhibit the late mineralocorticoid response, without interaction with the early response.

Developmental stage-specific expression of cyclic adenosine 3',5'-monophosphate response element-binding protein CREB during spermatogenesis involves alternative exon splicing.

Spermatogenesis is a temporally regulated developmental process by which the gonadotropin-responsive somatic Sertoli and Leydig cells act interdependently to direct the maturation of the germinal cells. The metabolism of Sertoli and Leydig cells is regulated by the pituitary gonadotropins FSH and LH, which, in turn, activate adenylate cyclase. Because the cAMP-second messenger pathway is activated by FSH and LH, we postulated that the cAMP-responsive element-binding protein (CREB) plays a physiological role in Sertoli and Leydig cells, respectively. Immunocytochemical analyses of rat testicular sections show a remarkably high expression of CREB in the haploid round spermatids and, to some extent, in pachytene spermatocytes and Sertoli cells. Although most of the CREB antigen is detected in the nuclei, some CREB antigen is also present in the cytoplasm. Remarkably, the cytoplasmic CREB results from the translation of a unique alternatively spliced transcript of the CREB gene that incorporates an exon containing multiple stop codons inserted immediately up-stream of the exons encoding the DNA-binding domain of CREB. Thus, the RNA containing the alternatively spliced exon encodes a truncated transcriptional transactivator protein lacking both the DNA-binding domain and nuclear translocation signal of CREB. Most of the CREB transcripts detected in the germinal cells contain the alternatively spliced exon, suggesting a function of the exon to modulate the synthesis of CREB. In the Sertoli cells we observed a striking cyclical (12-day periodicity) increase in the levels of CREB mRNA that coincides with the splicing out of the restrictive exon containing the stop codons. Because earlier studies established that FSH-stimulated cAMP levels in Sertoli cells are also cyclical, and the CREB gene promoter contains cAMP-responsive enhancers, we suggest that the alternative RNA splicing controls a positive autoregulation of CREB gene expression mediated by cAMP.