Expression of FGF2 and TGFalpha and testis morphology during testicular hypertrophy subsequent to hemicastration in the neonatal boar.

The objective was to ascertain fibroblast growth factor-2 (FGF2), epidermal growth factor (EGF), and transforming growth factor-alpha (TGFalpha) mRNA expression and testis morphology during accelerated testicular growth after hemicastration in the neonatal boar. On Day 10 after birth (Day 0), boars were assigned to control (n = 28), no treatment; hemicastrated (n = 28), left testis removed. The right testis in both groups (n = 7) was removed on Days 5, 10, 15, and 20. Expression of mRNA for FGF2, EGF, and TGFalpha was determined by qRT-PCR using TaqMan. Testicular morphology was determined on Day 15. On Day 10, hemicastrated boars had a greater (P = 0.01) testis weight (6.2 +/- 0.8 g; mean +/- SEM) than controls (4.3 +/- 0.4 g) and on Day 15 testis weight in hemicastrated boars (8.8 +/- 0.8 g) was twice (P < 0.01) that of control boars (4.2 +/- 0.3 g). Seminiferous tubule volume was approximately doubled in hemicastrated boars (P < 0.01) and was associated with an increase (P < 0.01) in Sertoli cell number. Interstitial compartment volume was greater (P < 0.01) in hemicastrated boars. Leydig cell numbers were similar (P = 0.14) but volume was greater (P < 0.01) for hemicastrates. There were no differences (P > 0.05) between control and hemicastrated boars in TGFalpha or FGF2 expression on Day 5 or Day 10, and EGF was not detected. It was concluded that upregulation of TGFalpha or FGF2 expression is not a pre-requisite for enhanced testicular growth and increased Sertoli cell proliferation that occurs subsequent to hemicastration in the neonatal boar.

Assessment of oxygenation and perfusion in the tongue and oral mucosa by visible spectrophotometry and laser Doppler flowmetry in healthy subjects.

UNLABELLED: Use of Visible Light Spectrophotometry (VLS) and Laser Doppler Flowmetry (LDF) is currently being studied by the authors to assess the viability of tissue margins in colon resection and to assess mucosal oxygenation in the colon. Thus, as a preliminary study it was necessary to evaluate whether there is any systematic inter-probe variability of the measurements by VLS and LDF. The oral mucosa was used as a model. METHODS: SO2 with VLS (Whitland Research RM200) and blood flow with LDF (Moor Instruments DRT4) were measured at 10 sites each on the tongue and oral mucosa of 10 healthy volunteers at 0, 6 and 24 hours using 3 different probes for VLS and 2 probes for LDF. RESULTS: The results showed that the SO2 measurements by VLS using the different probes on the tongue and mucosa were significantly correlated (P < 0.05). SO2 values at 6 hours were significantly higher than at 0 and 24 hours (P < 0.05) in all but one case. SO2 measurements were not correlated with LDF. LDF measurements by the 2 probes were correlated significantly (P < 0.05) but the standard deviations were very large. CONCLUSIONS: SO2 measurements on the oral mucosa are reproducible. Due to the large variations in LDF, VLS is likely to be the more clinically useful tool for identifying mucosal ischaemia.

Prediction of surgical site infections after major surgery using visible and near-infrared spectroscopy.

Final results of an investigation into whether oxygen saturation of tissues (StO2, measured by spectrophotometry) could predict surgical site infections (SSI) after major abdominal surgery are presented. StO2 was measured on the arm and wound site pre-operatively and then at 12, 24 and 48 hours post-operatively. A Whitland Research RM200 was employed as the visible lightguide spectrophotometer. StO2 measurements using this machine were designated SSO2 (skin SO2). A Hutchinson Inspectra Model 325 was used for the near infrared spectroscopy (NIS) measurements. StO2 measurements using this machine were designated MSO2 (muscle SO2). Of 59 patients (38 males, 21 females), 42 healed uneventfully and 17 developed SSI. The overall infection rate was 28.8%. No significant differences were seen in wound SSO2 between outcome groups at any stage. At 12 hours there was a significant difference between the two groups with respect to mean wound MSO2 (A = 58.3 +/- 21.6%, B = 42.2 +/- 16.6%, p = 0.005, 95% confidence interval = 5.26, 26.98). A receiver operating characteristic curve showed that when a wound MSO2 of 53% was chosen as the threshold to classify potential infection a sensitivity of 71% and a specificity 73% (chi-squared test, p = 0.002) was achieved. The use of the near-infrared spectrophotometry as a tool to predict wound infections should be further evaluated and advocated.

Cerebrocortical microcirculation in different stages of hypoxic hypoxia.

This study investigated the relation between local cerebrocortical oxygen tension (PO2) and cerebrocortical microflow (CMF) during normoxia (FiO2 = 0.3) and hypoxic hypoxemia (FiO2 = 0.16 and 0.1). Measurements were performed on mechanically ventilated rats and rabbits anesthetized with 0.8% Ethrane and maintained within normocapnic limits. Polarographic techniques based on the use of multiwire surface electrodes were applied for measurements of local PO2 and CMF. In both species the mean tissue PO2 values were similar under normoxia (26.0 and 31.5 mm Hg for rats and rabbits, respectively). CMF histograms showed pronounced heterogeneity. The highest CMF values exceeded the lowest ones by a factor of 36 in the rat and by a factor of 26 in the rabbit. Mean CMF values were 6.67 +/- 0.72 and 4.09 +/- 0.14 relative units (for definition see text) in rats and rabbits, respectively. During hypoxemia, if the mean tissue PO2 was greater than 5 mm Hg, mean CMF did not change but a change in the pattern of microflow distribution was observed with increases in some CMF values (up to 670% of control) and decreases in others (down to 12% of control). When mean tissue PO2 values of less than 5 mm Hg were observed during hypoxemia, mean CMF increased in both species by approximately 50% on average. The increase in CMF could be seen in each individual CMF recording. We conclude that in the brain cortex local regulatory mechanisms are responsible for the change in the pattern of distribution of microcirculation during moderate tissue hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic thermographic imaging for estimation of regional perfusion in the tuberculin reaction in healthy adults.

A sensitive method for measurement of the volume of blood flow through the skin, based on the kinetics of reheating after localised cooling, is described in this paper. This method has been used to study the tuberculin reaction as a model of cutaneous delayed-type hypersensitivity (DHS) in man. Over the positive reaction there is accelerated reheating similar in kinetics and extent to that seen after maximal hyperaemia induced by intradermal injection of histamine or prostaglandin E2. The earlier phase of reheating (10-100 s) is more dependent on blood flow, whereas the later phase (100-300 s) is apparently more dependent on non-perfusion heat exchange mechanisms, including conduction. The reheat kinetic method is largely dependent on blood flow in the deep dermal vessels (diameter > 50 microns), whereas the alternative approach of measurement of the velocity of flow of erythrocytes in the microcirculation by laser Doppler (LD) flowmetry gives results biased towards the most superficial dermal circulation. Previous studies with LD flowmetry have shown that the blood velocity is greatest at the centre of weak and strong reactions, while in the most intense reactions it is raised at the centre but maximal at the periphery (central relative slowing, CRS) raising the possibility of central ischaemia. The reheat kinetics approach has now indicated that the deep dermal circulation is not impaired in CRS reactions. It is concluded that there must be partial obstruction of the parts of the microcirculation communicating between the deep and superficial dermal plexuses, presumably from the accumulation of exudate oedema in the most intense tuberculin reactions.

Effect of hyperoxemia and ritanserin on skeletal muscle microflow.

Serotonin2 (5-HT2) receptor antagonists (ketanserin, ritanserin) can normalize a hyperoxemia-induced disturbance in skeletal muscle oxygenation, presumably by local microflow changes. The purpose of this study was to develop equipment for local hydrogen clearance measurements with a modified eight-channel platinum electrode to assess changes in local skeletal muscle capillary blood flow induced by hyperoxemia and ritanserin (0.035 mg/kg) during hyperoxemia. Laser-Doppler flowmetry was used for regional microflow measurements. Two groups of six anesthetized and artificially ventilated rabbits were studied: group I with normoxemia and hyperoxemia [arterial PO2 (PaO2) 48 kPa; 360 Torr] and group II before and after ritanserin with hyperoxemia (PaO2 46 kPa; 345 Torr). In group I, hyperoxemia induced a mean local hydrogen clearance decrease of 22% while laser-Doppler flowmetry signal decreased 31%. In group II, ritanserin induced a 125% mean local hydrogen clearance increase compared with hyperoxemia (or 37% compared with group I normoxemia); laser-Doppler flowmetry signal increased 30%. The sum distribution of local hydrogen clearances shifted to the left during hyperoxemia and to the right after ritanserin. The conclusion from this study is that local and regional microflow changes can explain the effects of hyperoxemia and ritanserin on skeletal muscle oxygenation.

Effect of hyperoxia at 1 and 2 ATA on hypoxia and hypercapnia in human skin during experimental inflammation.

Transcutaneous PO2 and PCO2 measurements and estimates of skin respiration were monitored at different levels of inspired PO2 in 20 healthy adults during the first 4 days of the tuberculin reaction, a convenient model of acute inflammation. Hyperoxia at 1 and 2 ATA significantly increased transcutaneous PO2 levels in undisturbed and in inflamed skin but did not fully correct the relative hypoxia at the site of inflammation. Hypercapnia was reduced with O2 breathing at 2 ATA. The apparent rate of O2 consumption at the reaction site was raised during hyperoxia, most prominently at 2 ATA. The most intense reactions showed a central relative slowing of laser-Doppler blood flow indicative of microcirculatory impairment. The extent of the relative hypoxia and hypercapnia was greatest in these strongest reactions. The density of lymphocytes and monocytes in biopsies of 48-h reactions was loosely related to the corresponding transcutaneous PO2 measurements. The present study provides evidence that diffusion barriers, in addition to increased local respiration, can contribute to the apparent hypoxia and hypercapnia of this inflammatory model.

A multiwire hydrogen electrode for in vivo use.

A multiwire surface electrode is described for measuring the partial pressure of hydrogen gas within extremely small volumes. The purpose was to record hydrogen clearance curves in vivo in order to analyse capillary blood flow. A method for improving the sensitivity and stability of the Clark-type polarographic sensor is presented. The in vitro and in vivo properties were investigated and are critically compared with the characteristics predicted from various models for the polarographic measurements of gases. The high stability and low drift of the electrode together with its small catchment volume (a hemisphere of radius 32 microns) meant that it could be reliably used for accurate, reproducible local measurements of hydrogen clearance curves in vivo. The experiments also demonstrated that the electrode could be used most successfully for the measurement of capillary blood flow even in the heart and contracting skeletal muscle.

Local hydrogen clearance as a method for the measurement of capillary blood flow.

A hydrogen clearance technique for the measurement of capillary blood flow in skeletal muscle (both resting and working) and the beating heart in experimental animals is described. Various methods for introducing the hydrogen into the region of measurement are compared, together with the appropriate methods for evaluating the resultant curves. All methods yielded results which were proportional to each other signifying that this is a reliable method for measuring changes in capillary blood flow. Reproducible results were obtained, and physiological changes in flow could be easily detected. An approach towards obtaining absolute flow values is proposed by simultaneous measurement of the arterial input function together with the independent use of other indicators.

Transcutaneous hydrogen clearance--a new non-invasive technique for assessing blood flow in human skin.

A new technique for the non-invasive assessment of skin blood flow is described using a modified, commercially available transcutaneous oxygen electrode. Initially, experiments were carried out on normal volunteers at skin temperatures of 40 degrees C and 44 degrees C. Transcutaneous H2 (tcpH2) clearances were measured after the subject had breathed a mixture of 2% H2 in air until a saturation value in the skin had been reached. tcpH2 clearance results were compared with laser Doppler flux values measured simultaneously on adjacent sites and at the same temperatures under control and reactive hyperaemic conditions. Good reproducibility for the tcpH2 technique and significant correlation (p < 0.002) between it and laser Doppler flux values at the same temperatures was demonstrated. In further experiments, (I125) 4-iodoantipyrine clearances (IAP) were carried out immediately prior to and at the same sites as tcpH2 clearances in critically ischaemic lower limbs. The correlation between the methods and the differences between tcpH2 values observed in normal and critically ischaemic skin were highly significant (p < 0.002).

A preliminary assessment of laser Doppler perfusion imaging in human skin using the tuberculin reaction as a model.

Laser Doppler imaging is a new development in the field of laser Doppler flowmetry. We were recently loaned the Lisca laser Doppler perfusion imager (LDI) manufactured by Lisca Development, Linkoping, Sweden for assessment against other methods for assessment of skin perfusion. In order to evaluate the device, it was applied to imaging flux changes induced in human skin during the tuberculin reaction. Flux values were compared directly with those from conventional lightguide laser Doppler flowmetry, and parameters measured using two other methods for assessment of tissue perfusion, dynamic thermographic imaging and tissue spectrophotometry. The results showed very good correlations between the various methods. In addition, the LDI showed that very large differences in flux values (up to 5 V) could be found within distances of only 2 mm during the tuberculin reaction and that focal centres of low flux values surrounded by higher values ('craters') could be found not only at the centre, but elsewhere in the lesion. The LDI enables rapid non-invasive detailed analysis of blood flow patterns in skin and correlates well with other methods for measuring skin perfusion. Its use to examine heterogeneity of microvascular blood flow patterns may lead to further understanding of the local mechanisms for regulation of oxygen supply to tissue.

Comparison of macro- and micro-lightguide spectrophotometric measurements of microvascular haemoglobin oxygenation in the tuberculin reaction in normal human skin.

The changes in haemoglobin oxygenation (SO2) occurring in the tuberculin reaction in human skin were measured using macro- and micro-lightguide spectrophotometry and the results compared. A significant difference was found between the measurements from the respective instruments, demonstrating that the micro-lightguide technique measures only in the most superficial capillaries. Laser Doppler flux (LDF) and transcutaneous oxygen (tcpO2) measurements were also obtained concurrently. At the height of the reaction, heating did not significantly change SO2 or LDF, showing that the vessels in the skin were maximally vasodilated. Although SO2 was increased in the reaction, tcpO2 decreased. This suggests that the infiltrating cells may present a diffusion barrier to oxygen between the capillaries and the tissue cells. This study has shown that micro-lightguide spectrophotometry gives a local picture of intracapillary oxygen supply, which is useful in elucidating the pathophysiological changes occurring during chronic inflammation.

Gender, age and carotid plaque morphology.

OBJECTIVES: To examine the relationship between patients gender, age and the development of different types of internal carotid artery plaque. DESIGN: Prospective open clinical study. METHODS: 455 carotid duplex scans with a greater than 50% stenosis were analysed in terms of gender, age, degree of stenosis symptoms and plaque morphology. RESULTS: There were 238 males (52.3%) and 217 females. Of 120 patients with type I plaque 86 were male (71.7%, chi 2 = 23.4, p = 0.000002). This high incidence of type I (haemorrhagic) plaque in men was accompanied by a higher degree of stenosis (chi 2 = 11.7 p = 0.0006) but was independent of the age of the patients and the presence of symptoms. CONCLUSIONS: Although this study supports the view that men have more severe carotid artery disease, it does not to affect a younger age group. The higher degree of stenosis and its association with haemorrhagic plaque is not translated into an increase in symptoms in men.

Tissue pH electrodes for clinical applications.

The reduction of peripheral blood flow, which occurs during shock or in patients with occlusive arterial disease of the lower limb is accompanied by an increase in hydrogen ion activity in tissue cells. If this change could be measured, it could possibly be used as an indicator of tissue perfusion in such patients. Investigations have been carried out into various pH microelectrode designs in order to construct one which could be used clinically to measure extracellular pH changes in skin. Experiments with antimony and externally insulated glass micro-electrodes demonstrated that these were unsatisfactory for the purpose. The successful design was insulated internally by means of a glass to glass fuse. It was robust, stable, sensitive and had a fast response time. Use of the electrode in normal volunteers produced reproducible skin pH values and demonstrated the feasibility of the system. Preliminary results using the micro-electrodes in patients indicate their possible application to the assessment of peripheral vascular disease, and to the monitoring of patients under intensive care.

Amputation level assessment using lightguide spectrophotometry.

The aim of this experimental study was to investigate whether lightguide spectrophotometry in the visible wavelength range in skin could be used to predict stump healing viability in patients with critical lower limb ischaemia. Remission spectra recorded at two sites (medial and lateral) on the line of a proposed trans-tibial amputation (TTA) and at 10mm intervals along the leg were analysed to give haemoglobin oxygenation (SO2). Degree of tissue hypoxia (DTH) along the leg was defined as the percentage of values along the leg less than 10% SO2. DTH and mean SO2 values were compared with skin blood flow values ((I125) 4-Iodoantipyrine clearance technique) and clinical outcome of trans-tibial amputation, (TTA) or trans-femoral amputation (TFA), in 41 patients. SO2 histograms were also measured in 12 normal subjects for comparison. The results of the study allowed the establishment of criteria for the accurate prediction of flap healing potential. Successful TTAs all displayed a minimum mean SO2 at the medial and lateral measurement sites of 30%, together with a maximum degree of tissue hypoxia of 15% along the limb. The combination of these criteria gave a sensitivity and selectivity of 1.0 for prediction of a successful outcome of TTA.