Low haemoglobin concentration in Tibetan males is associated with greater high-altitude exercise capacity.

Tibetans living at high altitude have adapted genetically such that many display a low erythropoietic response, resulting in near sea-level haemoglobin (Hb) concentration. We hypothesized that absence of the erythropoietic response would be associated with greater exercise capacity compared to those with high [Hb] as a result of beneficial changes in oxygen transport. We measured, in 21 Tibetan males with [Hb] ranging from 15.2 g dl(-1) to 22.9 g dl(-1) (9.4 mmol l(-1) to 14.2 mmol l(-1) ), [Hb], ventilation, volumes of O2 and CO2 utilized at peak exercise (V̇O2 and V̇CO2), heart rate, cardiac output and arterial blood gas variables at peak exercise on a cycle ergometer at ∼4200 m. Lung and muscle O2 diffusional conductances were computed from these measurements. [Hb] was related (negatively) to V̇O2 kg(-1) (r = -0.45, P< 0.05), cardiac output kg(-1) (QT kg(-1) , r = -0.54, P < 0.02), and O2 diffusion capacity in muscle (DM kg(-1) , r = -0.44, P<0.05), but was unrelated to ventilation, arterial partial pressure of O2 (PaO2) or pulmonary diffusing capacity. Using multiple linear regression, variance in peak V̇O2 kg(-1) was primarily attributed to QT, DM, and PCO2 (R(2) = 0.88). However, variance in pulmonary gas exchange played essentially no role in determining peak V̇O2. These results (1) show higher exercise capacity in Tibetans without the erythropoietic response, supported mostly by cardiac and muscle O2 transport capacity and ventilation rather than pulmonary adaptations, and (2) support the emerging hypothesis that the polycythaemia of altitude, normally a beneficial response to low cellular PO2, may become maladaptive if excessively elevated under chronic hypoxia. The cause and effect relationships among [Hb], QT, DM, and PCO2 remain to be elucidated.

Sea-level haemoglobin concentration is associated with greater exercise capacity in Tibetan males at 4200 m.

NEW FINDINGS: What is the topic of this review? Recent developments link relatively lower hemoglobin concentration in Tibetans at high altitude to exercise capacity and components of oxygen transport. What advances does it highlight? Haemoglobin concentration (ranging from 15.2 to 22.9 g dl(-1) ) in Tibetan males was negatively associated with peak oxygen (O2 ) uptake per kilogram, cardiac output and muscle O2 diffusion conductance. Most variance in the peak O2 uptake per kilogram of Tibetan males was attributed to cardiac output, muscle diffusional conductance and arterial partial pressure of CO2 . The mechanisms underlying these differences in oxygen transport in Tibetans require additional analyses. Despite residence at >4000 m above sea level, many Tibetan highlanders, unlike Andean counterparts and lowlanders at altitude, exhibit haemoglobin concentration ([Hb]) within the typical sea-level range. Genetic adaptations in Tibetans are associated with this relatively low [Hb], yet the functional relevance of the lower [Hb] remains unknown. To address this, we examined each major step of the oxygen transport cascade [ventilation (VE), cardiac output (QT) and diffusional conductance in lung (DL) and muscle (DM)] in Tibetan males at maximal exercise on a cycle ergometer. Ranging from 15.2 to 22.9 g dl(-1) , [Hb] was negatively associated with peak O2 uptake per kilogram (r = -0.45, P < 0.05) and both cardiac output (QT/kg: r = -0.54, P < 0.02) and muscle O2 diffusion conductance (DM/kg: r = -0.44, P < 0.05) but not ventilation, arterial partial pressure of O2 or pulmonary diffusing capacity. Most variance in peak O2 uptake per kilogram was attributed to QT, DM and arterial partial pressure of CO2 (r(2)  = 0.90). In summary, lack of polycythaemia in Tibetans is associated with increased exercise capacity, which is explained by elevated cardiac, muscle and, to a small extent, ventilatory responses rather than pulmonary gas exchange. Whether lower [Hb] is the cause or result of these changes in O2 transport or is causally unrelated will require additional study.

Increased blood-oxygen binding affinity in Tibetan and Han Chinese residents at 4200 m.

High-altitude natives are challenged by hypoxia, and a potential compensatory mechanism could be reduced blood oxygen-binding affinity (P50), as seen in several high-altitude mammalian species. In 21 Qinghai Tibetan and nine Han Chinese men, all resident at 4200 m, standard P50 was calculated from measurements of arterial PO2 and forehead oximeter oxygen saturation, which was validated in a separate examination of 13 healthy subjects residing at sea level. In both Tibetans and Han Chinese, standard P50 was 24.5 ± 1.4 and 24.5 ± 2.0 mmHg, respectively, and was lower than in the sea-level subjects (26.2 ± 0.6 mmHg, P < 0.01). There was no relationship between P50 and haemoglobin concentration (the latter ranging from 15.2 to 22.9 g dl(-1) in Tibetans). During peak exercise, P50 was not associated with alveolar-arterial PO2 difference or peak O2 uptake per kilogram. There appears to be no apparent benefit of a lower P50 in this adult high-altitude Tibetan population.

Neovascularisation after surgery for recurrent saphenofemoral incompetence: does surgical dissection technique matter?

BACKGROUND: The effect of the type of surgery on neovascularisation in the groin is unknown. The aim of the present study was to compare three different surgical techniques used for recurrent saphenofemoral incompetence in view of their effect on neovascularisation in the groin at short- and long-term follow-up after surgery. PATIENTS AND METHODS: 36 consecutive patients undergoing surgery for recurrent saphenofemoral incompetence were randomised. 12 patients underwent sharp dissection with knife or scissors and excision and ligation of scar tissue using absorbable suture material; 12 had dissection with electrocoagulation and 12 dissection with ultrasound (Ultracision Harmonic Scalpel). Clinical outcome was assessed using the venous clinical severity score and venous disability score, and the saphenofemoral junction was evaluated by means of duplex sonography three months and seven years after the operation respectively. If neovascularisation was present, the maximal diameter of new refluxing veins in the groin was measured. RESULTS: There was no statistically significant difference between the three surgical techniques. Duplex ultrasound showed neovascularisation with an average maximal diameter (± standard error) of the newly formed refluxing vessel of respectively 2.00 (± 0.63) mm, 1.00 (± 0.45) mm and 0.50 (± 0.50) mm after three months and 4.29 (± 1.41) mm, 3.32 (± 0.90) mm and 3.00 (0.83) mm after seven years (no significant difference between groups). After seven years no reflux was detected in 8/36 patients, no varicose veins were found in 14/36 patients. The patients were less symptomatic than before our redo operation and no one needed reoperation within the seven years. CONCLUSIONS: Dissection techniques in the groin did not influence the clinical and sonographic result at 3 months and at 7 years after redo surgery for recurrent varicose veins.

Truncular vascular malformations in a varicose vein surgery patient cohort.

BACKGROUND: To determine the incidence and significance of vascular malformations in a varicose vein surgery patient cohort in a prospective cohort study. PATIENTS AND METHODS: During a ten year time span we prospectively searched for patients with vascular malformations within a varicose vein surgery cohort. All patients underwent colour duplex sonography and surgery for symptomatic chronic venous disease or chronic venous insufficiency corresponding to clinical classes C2 to C6 according to CEAP. RESULTS: Five out of 1488 patients had truncular vascular malformations. One patient had an arterio-venous malformation in the groin. Venous malformations were found in three marginal veins and one bone perforating vein. Two of these five patients had a mitral valve prolapse syndrome, one a persistent foramen ovale, one had a bone cyst in a finger and one ectromelia of the hands and feet, respectively. No complications occurred following surgical treatment of these five malformations. CONCLUSIONS: Truncular arterio-venous and venous malformations in a varicose vein surgery patient cohort are rare. In our cohort the hemodynamic impact of the vascular malformations was low, the surgical treatment combined with varicose vein surgery resulted in technical and clinical success.

Primary surgery for sapheno-femoral incompetence: A randomised controlled trial to compare two techniques to reduce lymphatic complications.

BACKGROUND: We prospectively compared lymphatic complications after two types of surgery for primary sapheno-femoral incompetence: sharp dissection with meticulous ligation of lymphatic tissue and electrocoagulation technique respectively. PATIENTS AND METHODS: 154 consecutive patients undergoing surgery for bilateral primary sapheno-femoral incompetence were randomised. Each side was the control for the other side. 154 groins underwent sharp dissection with ligation of lymphatic tissue using absorbable suture material and 154 controls had a dissection performed with electrocoagulation. RESULTS: There was no lymphocoele, no relevant lymphorrhea and no extremity oedema in either group. Three patients had a minor lymphatic discharge in both groins, self-limiting within 24 hours (1.9%). There were no significant differences between the two groups. CONCLUSIONS: Lymphatic complications in primary surgery for sapheno-femoral incompetence are very rare. There is no detectable advantage of sharp dissection with ligation of lymphatic tissue over dissection with electrocoagulation without ligatures.

Tumors associated with superficial thrombophlebitis.

BACKGROUND: To assess the incidence of malignant tumors in patients with thrombophlebitis of the leg with regard to potential early tumor detection. PATIENTS AND METHODS: 140 consecutive patients were enrolled over a period of over 9 years in a retrospective follow-up study based on the electronic patient record. RESULTS: There were 18 patients (12.9%) suffering from thrombophlebitis in association with a malignant tumor: breast cancer in seven patients, colon carcinoma and haematologic cancer in four, skin cancer in three patients and one case each of oesophageal, prostatic, kidney and neck cancer . In two patients thrombophlebitis preceded the diagnosis of the malignancy. Superficial thrombophlebitis may have been associated in four cases (2.9%) with a benign tumor. CONCLUSIONS: Breast, colonic, haematological and skin cancer were mainly associated with superficial thrombophlebitis in our patients. In case of a thrombophlebitis without a known malignancy a thorough clinical examination with special regard to skin, breast and abdomen is mandatory.

Recurrence after surgery for varices in the groin is not dependent on body mass index.

OBJECTIVE: To investigate if the body mass index (BMI) differs between different groups of patients (incomplete ligation also defined as technical error, neo-revascularisation, uncertain and mixed) in recurrent same site inguinal varices after surgery (REVAS). METHODS: During a six and half year time span, we retrospectively analysed 203 consecutive procedures in 153 patients undergoing recurrent same site vein surgery in the groin. Individual BMI was calculated and compared within the different REVAS nature of the source groups. RESULTS: The median BMI was 28 for patients undergoing recurrent vein surgery in the groin with no relevant difference in BMI between the different source groups (confidence interval for the difference of adjusted group means equals [-1.5, 2.6]). CONCLUSIONS: There is no relevant difference in BMI between the two commonest REVAS groups. This may be due to small sample size, but confidence limits for difference of.

Sialyltransferase activity and hepatic tumor growth in a nude mouse model of colorectal cancer metastases.

Sialyltransferase activity (EC 2.4.99.6) was measured in the microsomal fraction of colorectal cancer cell lines using an assay based on the incorporation of [14C]CMP-sialic acid into asialofetuin. In the poorly differentiated lines MIP101 and Clone A, sialyltransferase activity had a Vmax of 0.36 and 0.31 nmol/mg protein/h, respectively, while the moderately differentiated to well-differentiated cell lines HT-29, CCL188, and CX-1 had Vmaxs of 2.46, 1.05, and 1.24 nmol/mg protein/h, respectively. All cell lines tested had a Km of 15.4 (+/- 0.7)(SD) mumol/liter. The better differentiated cells had higher levels of sialyltransferase activity, which correlated with their higher levels of sialic acid and their enhanced ability to form liver metastases in the nude mouse following intrasplenic injection compared to the poorly differentiated cell lines. Treatment of the cell lines with KI-8110, a CMP-sialic acid derivative which prevents incorporation of sialic acid into glycoconjugates, resulted in reduced formation of hepatic metastases by the colorectal carcinoma cell lines in the nude mouse model. It is suggested that reduced sialylation of adhesion molecules such as carcinoembryonic antigen may change the biology of the tumor cell, one consequence of which is the prevention of implantation of the cells into distant sites, resulting in a reduced incidence of metastases.

ras induced lesions in a heterotopic mouse bladder.

To determine the in vivo phenotype elicited in bladder epithelium following the expression of a ras oncogene we have introduced the HaSV ras transforming gene into transplants of normal urothelium. Stripped adult bladder mucosa incubated with HaSV, in the presence or absence of helper virus, was transplanted beneath the renal capsule of syngeneic animals and maintained for periods up to three months. Control implants, exposed to helper virus alone, formed heterotopic bladders lined by urothelium displaying focal areas of full differentiation when associated with underlying submucosal elements. Exposure of urothelium to HaSV resulted in increased proliferative potential of mucosal and submucosal elements with the appearance of a normal differentiated heterotopic bladder 10 days post-implantation. Implants left for 28 days presented a range of hyperplastic lesions (mild-severe) characterized from histological evaluation and antibody markers recognizing basal (D66) and superficial cell populations (H10) in normal bladder mucosa. Staining of mild hyperplastic lesions revealed an increased basal cell compartment and a loss of fully differentiated cells lining the lumen of the implanted bladder. In severe hyperplasia no superficial cells were observed but mucosal elements stained throughout with antibody D66. This phenotype was accompanied by an irregular laminin staining pattern associated with a disorganized basement membrane and increased blood vasculature. Similar experiments conducted with HaSV and helper virus resulted in the generation of mesenchymal lesions at 28 days with little surviving urothelium. The H-ras oncogenic protein can induce hyperplastic lesions in normal urothelium which were characteristic of preneoplastic changes identified in bladder carcinogenesis.

Follow-up after deep venous thrombosis in azygos continuation.

BACKGROUND: To determine the sequelae of patients after deep venous thrombosis inpatients with azygos continuation defined as agenesis of the inferior vena cava with collateral flow. PATIENTS AND METHODS: Five patients post deep venous thrombosis in the context of azygos continuation were followed up clinically and with colour duplex ultrasonography. RESULTS: All five patients had to our knowledge after the initial deep venous thrombosis no further thromboembolic events. Three patients after isolated iliac thromboses are symptom free or nearly symptom free, two after more extended thromboses still sufferfrom venous claudication. Four patients are without anticoagulation, one patient is permanently orally anticoagulated. CONCLUSIONS: Azygos continuation may not influence the risk of recurrent venous thrombo-embolism nor the outcome of a deep venous thrombosis. Careful deep venous thrombosis prophylaxis in patients with azygos continuation may be sufficient when a risk factor is present but conclusions lack due to the small numbers of patients of enough supportive data.

Metastatic potential of human colon cancer cell lines: relationship to cellular differentiation and carcinoembryonic antigen production.

The relationship between cellular differentiation and carcinoembryonic antigen (CEA) production by human colorectal tumor cells and their ability to form hepatic metastases was studied. Eight human colon cancer cell lines were injected into athymic mice using different routes of administration to characterize their metastatic potential. The four poorly differentiated, non or low CEA producing cell lines were poorly metastatic to the liver after intrasplenic injection. After intraperitoneal implantation the same cell lines were highly tumorigenic, and subsequently metastatic to the liver. In contrast, the four moderate to well-differentiated cell lines that produced moderate to high levels of CEA were highly metastatic to the liver following intrasplenic injection. After intraperitoneal implantation they were less tumorigenic, and metastatic to the liver. We conclude that in this system poorly differentiated non or low CEA producing colorectal cell lines have a lower metastatic capacity compared to the well-differentiated high CEA producing colorectal cell lines. These data correlate directly with the pattern of metastatic spread and clinical course observed in patients with these tumors, suggesting that degree of differentiation and level of CEA production may play a role in development of site-specific metastases.

Acquired and naturally occurring resistance of thyroid follicular cells to the growth inhibitory action of transforming growth factor-beta 1 (TGF-beta 1).

While the multifunctional proteins of the transforming growth factor-beta (TGF-beta) family have a potent antiproliferative effect on thyroid follicular cell growth, increased expression of TGF-beta in proliferating thyroid cells and in thyroid tumours has recently been described, suggesting a secondary counter-regulatory role of these proteins. We have studied further this apparent paradox in vitro using FRTL-5 cells, 5 continuous cell strains from feline multinodular goitres (MNG) and 29 primary cultures prepared from human MNG. While dose dependent inhibition of FRTL-5 cell growth was confirmed, a variable fraction of these cells was naturally resistant towards TGF-beta 1, thus explaining the large interassay variability of growth inhibition (36 to 98% within 2 days, n = 19). After 40 days of continuous exposure, FRTL-5 cells became fully refractory towards TGF-beta 1 inhibition, due to the selective growth of naturally resistant subclones, as demonstrated for example by microscopic observation of three-dimensionally growing collagen-embedded cell clusters. The refractoriness could still be demonstrated even after several cell passages. In addition, 2 out of 5 feline thyroid cell strains obtained from feline MNG and 18 out of 29 primary cultures from human MNG showed a high degree of refractoriness towards TGF-beta. We conclude that constitutively TGF-beta resistant cells may occur in thyroid glands and that persistent TGF-beta refractoriness may secondarily be acquired. Resistant cells may escape regular growth control mechanisms and hence may contribute to the notorious heterogeneity of thyroid growth and to nodular transformation.

Low intrathyroidal iodine concentration in non-endemic human goitres: a consequence rather than a cause of autonomous goitre growth.

Iodine may have an inhibitory and, in some circumstances, a stimulatory effect on thyroid follicular cell growth. Exogenous iodine deficiency causes the growth of endemic goitres and it has been claimed that low intrathyroidal iodine stores stimulate growth. On the other hand, the role of iodine, if any, in regulating the growth of human nodular goitres exposed to an ample supply of iodine has not been studied systematically. Very few data on intrathyroidal iodine concentration in this type of goitre are available. In the present work we have investigated total iodine content in 24 samples from 11 clinically and histomorphologically well-defined fast and autonomously growing human nodular goitres from a non-endemic area. Iodine was fractionated into thyroglobulin-iodine and non-thyroglobulin-iodine. The regional distribution of intrathyroidal iodo-compounds was also assessed in three goitres. Total iodine concentration, as well as its sub-fractions, i.e. thyroglobulin-iodine and non-thyroglobulin-iodine, were significantly lower than in normal thyroids. Furthermore, there was large inter- and intraindividual heterogeneity of all iodo-compounds as well as of thyroglobulin. Total iodine concentration varied by a factor of almost 40 between different goitre samples and by a factor of 20 between samples taken from the same goitre. Total non-thyroglobulin-iodine, the only fraction comprising possible cell growth-regulating iodo-compounds, varied by a factor of > 60 between different goitres and by a factor of > 6 between different samples of the same goitre. The low iodine concentration in all our goitre samples did not differ from values reported in the literature for endemic iodine-deficient goitres. Since all goitres studied here were actively growing while exposed to an ample supply of iodine, iodine shortage cannot be a primary and causal factor for the growth of this type of sporadic goitre. Rather, the low concentration and the large inter- and intraindividual heterogeneity of all iodo-compounds appear to be secondary incidental events well explained by the recently developed concept of autonomous thyroid growth.

Follicle-forming cat thyroid cell lines synthesizing extracellular matrix and basal membrane components: a new tool for the study of thyroidal morphogenesis.

Interactions between follicular epithelial cells and extracellular matrix (ECM) are supposed to play an important role in the development and maintenance of thyroid tissue architecture. In the present study we have therefore investigated the synthesis of ECM components by a feline thyroid cell line which is able to form follicle-like structures in vitro, and also in v-ras-transfected and control-transfected sublines. Transfections were performed by lipofection with pZSR (viral Harvey ras gene; neo) and pSV2-neo (control, neo only) plasmids. We have adapted a semisolid culture system composed exclusively of polymerized alginate and therefore devoid of ECM components. Feline cells embedded in alginate gels as single cells and cultured for up to 90 days formed cell clusters within 10 days. Follicle-like structures were formed in the original cell lines and also in the v-ras- and control-transfected cells. Differences in proliferation rates were observed, the v-ras-transfected cells growing up to two to three times faster than the non-transfected cells. Immunostaining was done using rabbit first antibodies directed against mouse collagen IV, human fibronectin, laminin (tumor Engelbreth-Holm-Swarm laminin), perlecan and other ECM components. For comparison, immunostaining was also performed on cryosections of nodular goiters of six hyperthyroid cats. The cell lines and their transfected clones stained strongly positive for collagen IV and fibronectin, and positively but less strongly for laminin and perlecan. The cat goiter tissue stained positively for collagen IV, laminin, perlecan, and fibronectin, and positive staining for S-laminin (containing the beta2-chain) was seen in blood vessel walls in this tissue. In conclusion, cat cell lines grow three-dimensionally in alginate beads over several weeks, they form follicle-like structures and express the same ECM components as the native cat goiter tissue. Transfection with v-ras does increase proliferation rate, but does not fundamentally alter formation of follicle-like structures and ECM expression. Alginate gel culture is a promising new tool for the study of follicular morphogenesis, polarity, the expression pattern of ECM components and of the interaction between thyrocytes and ECM. It avoids interference caused by gels composed of ECM components.

Preneoplastic lesions induced by myc and src oncogenes in reconstituted mouse bladder.

To define a role for different oncogenes in bladder neoplastic progression we have introduced viral myc and src oncogenes, singly or in combination, into intact normal urothelium. After incubation with virus, infected mucosa was heterotransplanted under the renal capsule of syngeneic animals and monitored for progression toward malignancy by use of histologic and immunofluorescence techniques. Although v-myc alone induced focal hyperplastic change, more dysplastic lesions were observed after expression of the src oncogene product in urothelial implants. In contrast, lesions induced by myc and src acting cooperatively were highly proliferative, displaying evidence of tumor formation within the 6-week study period. The presence and expression of myc and src oncogenic proteins, associated with preneoplastic and neoplastic lesions, was confirmed by use of Southern blot analysis and an immune complex kinase assay, respectively. These results indicate the formation of histologically distinct preneoplastic change elicited by the action of a single oncogene with induction of neoplastic changes when such oncogenic elements act cooperatively. This model provides an opportunity to study the action of different oncogenes throughout bladder neoplastic progression in vivo.

Effects of crocetin on pulmonary gas exchange in foxhounds during hypoxic exercise.

The carotenoid compound crocetin has been hypothesized to enhance the diffusion of O(2) through plasma, and observations in the rat and rabbit have revealed improvement in arterial PO(2) when crocetin is given. To determine whether crocetin enhances diffusion of O(2) between alveolar gas and the red blood cell in the pulmonary capillary in vivo, five foxhounds, two previously subjected to sham and three to actual lobectomy or pneumonectomy, were studied while breathing 14% O(2) at rest and during moderate and heavy exercise before and within 10 min after injection of a single dose of crocetin as the trans isomer of sodium crocetinate (TSC) at 100 microg/kg iv. This dose is equivalent to that used in previous studies and would yield an initial plasma concentration of 0.7-1.0 microg/ml. Ventilation-perfusion inequality and pulmonary diffusion limitation were assessed by the multiple inert gas elimination technique in concert with conventional measurements of arterial and mixed venous O(2) and CO(2). TSC had no effect on ventilation, cardiac output, O(2) consumption, arterial PO(2)/saturation, or pulmonary O(2) diffusing capacity. There were minor reductions in ventilation-perfusion mismatching (logarithm of the standard deviation of perfusion fell from 0.48 to 0.43, P = 0.001) and in CO(2) output and respiratory exchange ratio (P = 0.05), which may have been due to TSC or to persisting effects of the first exercise bout. Spectrophotometry revealed that TSC disappeared from plasma with a half time of approximately 10 min. We conclude that, in this model of extensive pulmonary O(2) diffusion limitation, TSC as given has no effect on O(2) exchange or transport. Whether the original hypothesis is invalid, the dose of TSC was too low, or plasma diffusion of O(2) is not rate limiting without TSC cannot be discerned from the present study.

Inhibition of sialic acid incorporation prevents hepatic metastases.

It has been hypothesized that the metastatic capacity of tumors may be correlated with hypersialylation of the cell surface. We used a novel inhibitor of sialic acid incorporation, KI-8110, to determine the effect of depletion of cell surface sialic acid on the metastatic behavior of three human colorectal cancer cell lines, in which hepatic seeding was related to tumor cell differentiation. Treatment of tumor cells with KI-8110 prior to intrasplenic injection prevented liver colonization. Total cellular sialic acid was reduced, as was that of the cell surface. Secreted forms of carcinoembryonic antigen also were depleted of sialic acid by this treatment. These data show that depletion of sialic acid from cell surface glycoconjugates reduces the incidence of hepatic metastases from human colorectal primary tumors and adds to the mounting evidence of the importance of sialic acid in determining the biological behavior of tumor cells.

Model of the athymic nude mouse for the study of benign goiter disease.

Since Shimosato et al., in the mid 70s transplanted for the first time thyroid carcinoma tissue onto nude mice, other research groups have made use of the nude mouse model for the investigation of xenotransplanted thyroid tissue. The use of this model for the investigation of benign goiters is briefly discussed in this article. Normal human thyroid tissue has been transplanted either as a control in experiments with benign and malignant goiter tissue, or for the study of thyroid tissue response to stimulators such as TSH or thyroid stimulating antibodies (TSAb). Thyroid glands from 8- to 10-week old human fetuses obtained at the time of legal abortion were cryopreserved in liquid nitrogen and successfully transplanted into nude mice. Moreover, all the variants of human benign goiter tissue have been xenotransplanted: tissue from nodular and diffuse goiters, hot and cold nodules or goiter areas, rapidly growing nodules, etc. Two examples of animal thyroid tissue xenotransplantation onto nude mice are briefly discussed: Nude mice bearing normal thyroid tissue transplants from 4 different species (man, rat, pig, guinea-pig) have been used for the study of the species specific effect of bovine TSH and TSAb. In studies aiming at elucidating the pathogenesis of hyperthyroidism, toxic goiter tissue from hyperthyroid cats has been transplanted. In methodological terms, these experiments have shown that surgically removed goiter tissue can be shipped by air in cell culture medium at 4 degrees C over long distances and then successfully transplanted.-Finally, cell lines such as the rat cell line FRTL-5 can be transplanted onto nude mice either as cell suspension or embedded in collagen, for example for the study of proliferation and folliculogenesis. Using the xenotransplantation model, function and proliferation, morphogenesis and differentiation, as well as thyroid autonomy and response to stimulators have all been studied in xenotransplanted human and animal thyroid thyroid tissue and cell lines under various experimental conditions. Although new research tools, for example transgenic animals, are now increasingly and successfully used, xenotransplantation still offers the possibility of addressing some specific questions which cannot be answered so easily with other experimental models. For example, studies with human tissue, involving drugs or radioactive tracers which cannot be applied to the intact human being, can relatively easily be performed with xenotransplanted human tissue and application of the drug or tracer to the host mouse. Or embryological development can be followed and studied using fetal thyroid (and other) tissue transplanted onto nude mice; here, of course, difficult ethical issues have to be considered. Finally, it should be mentioned that, although many scientific questions can be studied nowadays by cell culture or other in vitro systems, animal models are still needed. Extrapolation to the human being, however, should always be done with caution and we should always keep in mind that for the understanding of a human disease indeed human experimental models remain the goldstandard.

A randomized controlled trial to determine the effect of humidified carbon dioxide (CO2) insufflation on postoperative pain following thoracoscopic procedures.

BACKGROUND: It has previously been shown that the insufflation of humidified gas during laparoscopy results in less postoperative pain than is observed following the use of dry gas. Experimental evidence also suggests that dry gas insufflation during thoracoscopy results in greater structural injury to the pleura than occurs with the use of humidified gas. The present study was designed to determine the effect of humidified gas insufflation on postoperative pain following thoracoscopic procedures. METHODS: Forty consecutive patients were prospectively randomized. Twenty patients were insufflated with humidified carbon dioxide (CO(2)), and 20 control patients received standard dry CO(2). RESULTS: The patients' analogue pain score was significantly lower following humidified gas insufflation compared to dry gas insufflation when assessed at 6 h postoperatively, as well as on the 1st, 2nd, 3rd, and 14th postoperative days. The postoperative morphine consumption was lower in the humidified group than it was in the control group. The incidence of respiratory complications was identical for both groups. CONCLUSION: The use of humidified gas appears to reduce postoperative pain but not the rate of respiratory complications.