[Reliabilty of intraoperative recurrent laryngeal nerve monitoring in thyroid surgery]

INTRODUCTION

The intraoperative monitoring of the recurrent laryngeal nerve (NLR) is increasingly used in thyroid surgery. What has the surgeon to know about reliability and peculiarity of this method?

PATIENTS AND METHOD

Between 11/98 and 3/01 417 patients were operated for thyroid pathology. Vocal cord function was controlled pre- and postoperatively in all cases by laryngoscopy. Intraoperative electromygraphic NLR identification and postoperative vocal cord function were registered prospectively.

RESULTS

Intraoperative NLR identification succeeded in 98.9 % (776/784 nerves at risk). Minor vocal cord dysfunctions were demonstrable for less than 4 weeks in 13 patients (1.6 %) associated with edema or hematoma in 11/13 cases. Complete unilateral NLR pareses was seen laryngoscopically in 16 patients (2 %). 1 patient revealed a malignant NLR infiltration. Electromygraphic NLR identification wasn't possible and followed by postoperative NLR palsy in 2 patients. In 11/13 cases with a regular intraoperative monitoring postoperative vocal cord function recovered within 8 weeks. In 2 of 4 NLR pareses persisting at the moment the follow up is longer than 12 months (permanent palsy rate 0.25 %).

CONCLUSIONS

NLR identification during thyroid surgery is improved by intraoperative monitoring. In cases with difficult thyroid preparation the vagal nerve may be stimulated for indirect proof of NLR integrity.

[Muir-Torre syndrome]

The Muir-Torre syndrome (MTS) is an autosomal dominant disease defined by the coincidence of at least one sebaceous skin tumor and one internal malignancy. We describe an additional case and give a review of the literature. Over a period of 7 years, 19 skin tumors were excised in a 50 year old male patient. A total of 3 colonic carcinomas, one gastric carcinoma and one laryngeal carcinoma were operated successfully. The underlying defective mutation in the hMSH2 gene and the microsatellite instability were demonstrable. MTS is graded as a subgroup of hereditary non-polyposis colorectal cancer (HNPCC). In patients with MTS and with family members with known defective mutation, regular follow-up and search for new malignancies are mandatory.

[Esophageal perforation. Etiology, diagnosis, therapy]

METHOD

Between 10/1997 and 2/2000 we treated eight patients (-66.5 y, 31-92 y, 5 male, 3 female). These cases were analyzed retrospectively.

RESULTS

In one case the the perforation was located in the cervical part, in three cases in the intermediate part, and in four cases in the distal part oesophagus. In seven cases the perforation was caused by endoscopic and one acid burn in suicidal intention. Surgical treatment was performed in seven cases (87.5%), five of them with primary suture, two with primary esophageal resection. The mortality rate was 50%. There was no insufficiency of the suture, but two patients died because of pulmonary complications, one patient with known hepatic cirrhosis (Child C) because of an uncontrollable bleeding of his fundus and esophageal complications 5 days after successful surgical treatment, and one patient because of fulminant sepsis after dislocation of an enteral catheter. Three of the patients were operated within 12 hours after perforation, seven of them were operated within less than 24 hours.

CONCLUSIONS

Surgical treatment of esophageal perforation within 24 hours after perforation shows good results. The outcome of the treatment depends on whether there are postoperative pulmonary complications and concomitant diseases. Enteral nutrition should be avoided in cases of primary esophageal resection to facilitate the surgical reconstruction at the second operation.

[Hemithyroidectomy on principle in cases of unclear fine needle biopsy and frozen section findings]

SUMMARY

Fine needle aspiration biopsy (FNB) and frozen section (FS) may help to validate pre- and intraoperatively dignity of thyroid nodules. Credibility and clinical valuation of both methods have to be taken into consideration of surgical treatment. Between 7/96 and 6/00 82 patients were operated for thyroid lesions using both diagnostic methods to verify thyroid lesions. The sensitivity of both methods is low. With FNB only 5/11 malignancies (45.5 %) were recognized. Within the group of "suspicious" FNB findings (22/82; 26.8 %) definitive histology demonstrated another 6 carcinomas. Only 1 of these initially not recognized carcinomas was verified by FS intraoperatively whereas 5 carcinomas were judged to be benign lesions. Follicular carcinomas and follicular variants of papillary carcinomas could not be assessed by FNB in 6/8 and by FS in 8/9 cases. Only very few malignancies, which are not found by FNB, can be verified by FS. A routine use of intraoperative FS to verify FNB results is not justified, but can give additional information about tumor size, lymph node status and extra-/intrathyroid nodules, which are not examined by FNB preoperatively. Hemithyroidectomy with lymph node dissection represents the operation of choice in cases with unclear FNB results to avoid a second operation with increased risk of recurrent nerve palsy and hypoparathyroidism.

[Gastrointestinal autonomic nerve tumor]

Gastrointestinal autonomic nerve tumors (GAN-tumor) are rare malignant neurogenic stromal tumors of the intestinal tract. The origin is suspected in the autonomic nerve plexus Meissner or Auerbach with the interstitial cells of Cajal as precursors. We report on a 53-year-old patient with a clinical apparent and radiological 5 cm measuring tumor of the jejunum, which was resected and immunohistochemically verified as GAN-tumor. Within the follow-up of 29 months metastases appeared within the omentum majus with a diffuse peritoneal spreading. Several trials of adjuvant chemotherapy (adriamycine/ifosamide, taxotere, gemcitabine/xyloda) were ineffective. 15 months after the second operation the patient died. Since the first description of the GAN-tumor in 1984 87 patients were reported in the literature. No recurrences or metastasis were seen in tumors with a seize less than 5 cm. A tumor seize of more than 10 cm is associated with recurrences in 64% of the cases within 2 years. Since there is no option for medical treatment, surgical resection is the treatment of choice and has to be considered also in the case of recurrence.

[The Limberg transposition flap in surgical therapy of chronic pilonidal sinus]

The operative treatment of pilonidal sinus is characterized by an increased rate of wound healing complications and late recurrences. The Limberg transposition flap is an easy method for covering the defect after excision of the pilonidal sinus. The flap smooths out the deep skin fold of the rima ani and counteracts in this manner an important pathogenetic factor of pilonidal sinus recurrence. Between 6/96 and 7/99 we treated 42 patients using this method without complications of wound healing or recurrences. Comparison of literature results of different operative treatments (open granulation, primary suture, Z-plasty) shows lessened complication and recurrence rates for the Limberg transposition flap, which is the method of choice for chronic pilonidal sinus nowadays.

[Terminal sigmoid anus praeter. Operative technique and surgical complications]

Every complication of the sigmoid stoma means a restriction of patients' quality of life. The complications of 164 patients were analyzed retrospectively (1/1996-5/1999). Indications for creation of a sigmoid stoma were malignomas of the rectum (n = 109). Hartmann's operation with or without sigmoid resection was performed in 55 patients for different reasons. Reoperation for complications was necessary in 8 patients (4.9%). Stenosis of the stoma (n = 3) and peristomal hernia (n = 2) were the most frequent complications. Other indications for reoperation were a prolapse (n = 1) of the stoma, a peristomal abscess with consecutive cutaneous necrosis (n = 1) and a metastasis of rectal cancer at the stoma site (n = 1). Operation techniques for sigmoid stoma creation and its complications are described. The own operative results are completed in an optimal manner by the work of a stoma therapist taking care of the patients both during and after hospital stay.

[Trans-sternal thymectomy. Surgical indications and perioperative management]

Between 1985 and 1998 42 transsternal thymectomies were performed. The median duration of symptoms in myasthenia gravis patients (n = 27, 25/27 patients in stadium I/II of the Ossermann classification) was 40.3 weeks and 70.8 days between first diagnosis and operation. In 12 patients a thymoma was found (11/12 patients with stadium I/II of Masaoka classification), which was associated with myasthenia gravis symptoms in 10 cases. In 3 patients thymic tumors of other origin were verified histologically. After surgery these patients have an increased risk of pulmonary complications. We changed 1996 the perioperative anesthesiological procedure using total intravenous anesthesia with propofol/remifentanil and systemic patient-controlled analgesia with piritramide in the first two days after transsternal thymectomy. This management allows a quick extubation after operation and improved lung function postoperatively.

High-pressure denaturation of apomyoglobin

The pressure denaturation of wild type and mutant apomyoglobin (apoMb) was investigated using a high-pressure, high-resolution nuclear magnetic resonance and high-pressure fluorescence techniques. Wild type apoMb is resistant to pressures up to 80 MPa, and denatures to a high-pressure intermediate, I(p), between 80 and 200 MPa. A further increase of pressure to 500 MPa results in denaturation of the intermediate. The two tryptophans, both in the A helix, remain sequestered from solvent in the high-pressure intermediate, which retains some native NOESY cross peaks in the AGH core as well as between F33 and F43. High-pressure fluorescence shows that the tryptophans remain inaccessible to solvent in the I(p) state. Thus the high-pressure intermediate has some structural properties in common with the apoMb I(2) acid intermediate. The resistance of the AGH core to pressures up to 200 MPa provides further evidence that the intrinsic stability of these alpha-helices is responsible for their presence in a number of equilibrium intermediates as well as in the earliest kinetic folding intermediate. Mutations in the AGH core designed to disrupt packing by burying a charge or increasing the size of a hydrophobic residue significantly perturbed the unfolding of native apoMb to the high-pressure intermediate. The F123W and S108L mutants both unfolded at lower pressures, while retaining some resistance to pressures below 50 MPa. The charge burial mutants, A130K and S108K, are not stable at very low pressures and both denature to the intermediate by 100 MPa, half of the pressure required for wild type apoMb. Thus a similar intermediate state is created independent of the method of perturbation, and mutations have similar effects on native state destabilization for both methods of denaturation. These data suggest that equilibrium intermediates that can be formed through different means are likely to resemble a kinetic intermediate.

Hypertonic/hyperoncotic resuscitation after intestinal superior mesenteric artery occlusion: early effects on circulation and intestinal reperfusion

The objective of the study was to determine the early effects of hypertonic/hyperoncotic starch resuscitation after 2 h occlusion of the superior mesenteric artery (SMA) in comparison to animals reperfused without treatment and isotonic resuscitation. SMA was clamped (18 pigs, 19-23 kg) for 2 h followed by a 2-h reperfusion period, which was initiated with isotonic (ISO) (35 mL/kg 0.9% NaCl and 5 mL/kg 10% hydroxyethyl starch within 30 min) or hypertonic/hyperoncotic resuscitation (HHES) (7.5% NaCl/10% hydroxyethyl starch within 5 min). Cardiac output (CO), mean arterial blood pressure (MAP), serum lactate, antimesenteric serosal Laser-Doppler values (LD), and intramural pHi (tonometry) were measured. Without resuscitation at the onset of reperfusion MAP (70 +/- 3 mmHg) decreased to 40 +/- 3 mmHg and CO to 31% of baseline values after 30 min. Serum lactate increased to 5.1 +/- 1.6 mmol/L without improvement. The decrease of CO was attenuated only during the initial 30 min of reperfusion in the ISO group, but significantly better counteracted by hypertonic/hyperoncotic resuscitation. Without treatment, LD flow of the ileum (baseline 23-27 LD units) recovered but intramural pH (pHi) remained significantly decreased (7.26 +/- 0.05). With isotonic resuscitation LD values (21.8 +/- 2.1 LD units) and intramural pHi (7.09 +/- 0.14) decreased even more (P < 0.05) whereas the HHES group showed a significant hyperemic reaction and a normalization of the intramural pHi and serum lactate within 30 min. Hypertonic/hyperoncotic resuscitation significantly improves MAP and CO during reperfusion shock and induces an immediate hyperemic reperfusion reaction of the intestinal microcirculation. Adequate isotonic fluid replacement in order to restore the postischemic plasma volume loss may cause a pronounced deterioration of intestinal perfusion.

[Intraoperative electromyographic identification of the recurrent laryngeal nerve]

BACKGROUND

Recurrent nerve palsy is the most important complication of thyroid surgery. Correct identification of the nerve during the surgical procedure is essential to avoid damage.

METHOD

We evaluated the intraoperative electromyographic identification procedure of the recurrent laryngeal nerves in 77 consecutive patients. The operations performed were 63 subtotal resections, 6 hemithyroidectomies, 4 hemithyroidectomies in combination with subtotal resection of the opposite side and 4 thyroidectomies.

RESULTS

Identification of the recurrent laryngeal nerve by electrophysiologic nerve stimulation was successful in 97.4%. Recurrent nerve palsy was not seen in postoperative laryngoscopic control.

CONCLUSIONS

Intraoperative electromyography improves the identification rate of the recurrent laryngeal nerve and allows electrophysiologic verification of nerve function as a result of injury to the thyroid.

Quantitative analysis of visual field and optic disk in glaucoma: retinal nerve fiber bundle-associated analysis

BACKGROUND

A study was performed to evaluate whether visual field analysis using a perimetric nerve fiber bundle map gives information additional to global visual field indices and cumulative defect curves for early glaucoma diagnosis.

METHODS

One hundred and four control subjects, 124 patients with ocular hypertension (OHT), 97 patients with high-tension glaucoma without visual field defects (preHTG) and 91 patients with open-angle glaucoma with visual field defects [30 low-tension glaucoma (LTG), 61 high-tension glaucoma (HTG)] were included in this study. Correlation analyses were performed between (a) global visual field indices and total neuroretinal rim (NRR) area; (b) local mean values of four visual field areas and the NRR area of the corresponding four optic disk sectors; and (c) local mean values of 10 perimetric nerve fiber bundles (PNFB 1-10) according to Weber and Ulrich (1991) and the four optic disk sectors. The correlations were adjusted for global mean defect and total NRR.

RESULTS

There were no significant correlations between NRR area and visual field in control subjects or in patients with OHT or preHTG for all three analyses. Significant correlations were found between the global visual field indices and the total NRR area for LTG and HTG. Significant correlations between local mean defects and NRR area of corresponding optic disk sectors were found only in LTG for the superior and inferior visual field area and the PNFB covering these areas.

CONCLUSION

The method used for visual field analysis and sectorization of the optic disk does not give additional information on visual field defects in patients with normal global visual field indices and a normal cumulative defect curve. The nerve fiber bundle-related visual field analysis allows the topographical determination and quantification of glaucomatous damage.

Neuromonitoring of the external branch of the superior laryngeal nerve during thyroid surgery

Changes of the voice caused by injury of the external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery may have essential consequences for a patient's life. Therefore, intraoperative effort has to be made to prevent EBSLN damage. Neuromonitoring has already been described as helpful to improve the identification rate of the recurrent laryngeal nerve. We describe our surgical procedure of upper thyroid pole preparation using neuromonitoring to avoid intraoperative damage of the superior laryngeal nerve. Neuromonitoring allowed safe preparation of the upper thyroid pole without injury of the ESBLN in 108 consecutive patients.

Effects of high pressure and temperature on the wild-type and F29W mutant forms of the N-domain of avian troponin C

The N-domain of troponin C (residues 1-90) regulates muscle contraction through conformational changes induced by Ca2+ binding. A mutant form of the isolated domain of avian troponin C (F29W) has been used in previous studies to observe conformational changes that occur upon Ca2+ binding, and pressure and temperature changes. Here we set out to determine whether the point mutation itself has any effects on the protein structure and its stability to pressure and temperature in the absence of Ca2+. Molecular dynamics simulations of the wild-type and mutant protein structures suggested that both structures are identical except in the main chain and the loop I region near the mutation site. Also, the simulations proposed that an additional cavity had been created in the core of the mutant protein. To determine whether such a cavity would affect the behavior of the protein when subjected to high pressures and temperatures, we performed 1H-NMR experiments at 300, 400, and 500 MHz on the wild-type and F29W mutant forms of the chicken N-domain troponin C in the absence of Ca2+. We found that the mutant protein at 5 kbar pressures had a destabilized beta-sheet between the Ca2+-binding loops, an altered environment near Phe-26, and reduced local motions of Phe-26 and Phe-75 in the core of the protein, probably due to a higher compressibility of the mutant. Under the same pressure conditions, the wild-type domain exhibited little change. Furthermore, the hydrophobic core of the mutant protein denatured at temperatures above 47 degrees C, while the wild-type was resistant to denaturation up to 56 degrees C. This suggests that the partially exposed surface mutation (F29W) significantly destabilizes the N-domain of troponin C by altering the packing and dynamics of the hydrophobic core.

High-resolution, high-pressure NMR studies of proteins

Advanced high-resolution NMR spectroscopy, including two-dimensional NMR techniques, combined with high pressure capability, represents a powerful new tool in the study of proteins. This contribution is organized in the following way. First, the specialized instrumentation needed for high-pressure NMR experiments is discussed, with specific emphasis on the design features and performance characteristics of a high-sensitivity, high-resolution, variable-temperature NMR probe operating at 500 MHz and at pressures of up to 500 MPa. An overview of several recent studies using 1D and 2D high-resolution, high-pressure NMR spectroscopy to investigate the pressure-induced reversible unfolding and pressure-assisted cold denaturation of lysozyme, ribonuclease A, and ubiquitin is presented. Specifically, the relationship between the residual secondary structure of pressure-assisted, cold-denatured states and the structure of early folding intermediates is discussed.

A high-pressure, high-resolution NMR probe for experiments at 500 MHz

A novel high-pressure, high-resolution NMR probe is described which operates at a frequency of 500 MHz. The design features an alternative RF coil (8 mm sample tube) for high frequency, sensitivity, probe power, and resolution (< 3.0 x 10(-9)). The probe is capable of pressures to at least 5 kbar over a temperature range of -30 to 80 degreesC, and has a double-tuned 1H/2H circuit which can tune at 1H frequencies of either 300 or 500 MHz. The sensitivity of the 300-MHz circuit is over twice that of previous 10-mm high-pressure NMR probe designs, while at 500 MHz the sensitivity is nearly five times that of previous 300-MHz pressure probes. Potential biochemical applications are demonstrated by 2D NOESY spectra of a Troponin C mutant.

Structure of pressure-assisted cold denatured lysozyme and comparison with lysozyme folding intermediates

At high (> 3.5 kbar) pressures and low (< -10 degrees C) temperatures, hen egg-white lysozyme denatures readily and reversibly. Amide hydrogen exchange methods were used to investigate the structure of the pressure-assisted cold-denatured state of lysozyme. Protection factors were obtained for 52 backbone amide protons. The extent of protection of many of these protons is markedly different from that in lysozyme denatured by high temperature, high urea concentration, or chemical modification; specifically, the protection factors are higher and are strongly correlated with elements of secondary structure present in the native state. Furthermore, the pattern of protection factors is similar to that observed in lysozyme during refolding from highly denatured states, particularly during the early stages (< 3.5 ms) of refolding [Gladwin, S. T., & Evans, P. A. (1996) Folding Des. 1, 407]. Previous data on cold-denatured ribonuclease A were reevaluated and compared to known folding intermediates [Houry, W. A. & Scheraga, H. A. (1996) Biochemistry 35, 11734; Udgaonkar, J. B., & Baldwin, R. L. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 8197] to further test the supposition that the pressure-assisted cold-denatured states of proteins resemble the early folding stages.

[Are there genuine and pseudo-normal pressure glaucomas? Body position-dependent intraocular pressure values in normal pressure glaucoma]

BACKGROUND

Elevation of intraocular pressure in the supine position has been previously described in literature. Aim of this study is to investigate the elevation of intraocular pressure in normal tension glaucoma and its effect on the morphology of the optic disc, visual field function and capillary blood flow of the retina and optic disc.

PATIENTS AND METHODS

56 eyes of 28 preperimetric and advanced normal tension glaucoma patients were prospectively evaluated. Ten eyes of ten normal patients served as a control group for the measurements of the intraocular pressure. In the course of a 24-h pressure profile applanation tonometry was performed in the morning in a supine and three and ten minutes later in a sitting position with Draeger's and Goldmann's tonometers. Arterial blood pressure was measured at the same time. The optic disc's morphology was evaluated by stereo photographs and Laser Scanning Tomography. As a sensory test computer perimetry was used. Capillary blood flow was measured at defined areas of the retina and optic disc. An intraocular pressure above 21 mm Hg in the supine position was used as a criterium to define two groups of normal tension glaucoma patients.

RESULTS

In the supine position a statistically significant elevation of intraocular pressure was observed in 24 normal tension glaucoma patients by 6.2 +/- 2.8 mm Hg up to 21.8 +/- 3 mm Hg. Diastolic blood pressure in the supine position (80 +/- 10.5 mm Hg) was significantly lower than in the sitting position (94 +/- 11 mm Hg, p = 0.021). 12 of 28 normal tension glaucoma patients showed an intraocular pressure lower than 22 mm Hg in the supine position. In these patients a tendency towards a higher incidence for the occurrence of optic disc haemorrhages and significantly higher values for blood flow (p < 0.0005) and volume (p < 0.005) in the retina and optic nerve head could be shown. In this group of normal pressure glaucoma patients a higher incidence of migraine and vasospastic complaints was reported in the patients' history.

CONCLUSION

In this study some normal tension glaucoma patients showed intraocular pressures in the supine position higher than 21 mm Hg and a lower diastolic arterial pressure. The higher incidence of haemorrhages and higher values for flow and volume parameters of the optic disc in normal tension glaucoma patients with an intraocular pressure lower than 22 mm Hg implicate the existence of two entities: real and pseudo normal tension glaucomas.

Structure of the pressure-assisted cold denatured state of ubiquitin

The pressure-assisted cold denatured state of ubiquitin in aqueous solution was investigated by high resolution NMR. Hydrogen exchange kinetics were measured for backbone amide protons in the cold denatured protein to determine its structure. In contrast to cold denatured ribonuclease A and lysozyme, cold denatured ubiquitin shows little persistent secondary structure. The behavior of ubiquitin supports the idea of a relationship between the residual structure of pressure-assisted cold-denatured states and the structure of early folding intermediates provided they exist.

High-Resolution NMR Probe for Experiments at High Pressures

A 300 MHz high-resolution, high-pressure NMR probe which operates in the pressure range of 1 bar to 9 kbar at temperatures of -30 to 100&deg;C is described. Specialized novel design features of the probe are discussed and test spectra showing resolution better than 1 Hz (<3.0 x 10(-9)) for 8 mm samples are presented. Potential biochemical applications of this probe are illustrated by experiments dealing with the pressure-induced unfolding of hen egg white lysozyme.

Hydrogen-exchange kinetics in the cold denatured state of ribonuclease A

Ribonuclease A (RNase A) exhibits a well-defined cold denaturation transition when examined at high pressure (3 kbar) and low temperatures (below -10 degrees C). Our main interest in this study was to investigate the pressure-assisted cold denatured state of RNase A by hydrogen exchange techniques. The protection factors obtained from the kinetic data are similar to those obtained previously for RNase A denatured by exposure to high pressure near its temperature of maximum stability, but differ markedly from those in thermally denatured RNase A. A qualitative analysis of the hydrogen-exchange rates suggests that cold denatured RNase A behaves markedly differently from a random coil, probably due to patches of residual secondary structure.

[Reperfusion shock after occlusion of the superior mesenteric artery and accumulation of leukocytes within the wall of the small intestine]

The epithelial damage and the accumulation of the leucocytes within intestinal wall layers after ischemia and reperfusion was investigated in a pig model. Superior mesenteric artery (SMA) was occluded for 1 h (group 2, n = 9), 2 h (group 3, n = 6) and 3 h (group 4, n = 7) with a consecutive 2 h reperfusion period. The histological evaluation was performed on hematoxylin-eosine and Naphtol AS-D chloracetate stained preparations. The intensity of reperfusion shock depended on the duration of the intestinal ischemia. After 1 h SMA occlusion systolic blood pressure stabilized at a lower level with a normalization of the serum lactate level and the intestinal intramural pHi within the reperfusion period. After 2 h SMA occlusion the decrease of the systolic blood pressure was intensified (54-69 mm Hg) with a persistent elevated serum lactate concentration and a delayed increase of the ischemic pHi values. Reperfusion after 3 h SMA occlusion caused an irreversible shock. The epithelial damage also depended on the duration of the SMA occlusion. There were no significant changes of the leucocytic accumulation within the submucosa. But a significant increase of the number of the leucocytes was seen within the inner and the outer layer of the muscularis after 1 h SMA occlusion (106+/-5/mm2 resp. 280/mm2; p<0.05). This increase was less pronounced after 2 h (92+/-5/mm2*resp. 189+/-4/mm2; *p<0.05) and 3 h of SMA occlusion (84+/-5/mm2 resp. 185+/-23/mm2). Intestinal ischemia and reperfusion caused no changes of the leucocytic accumulation within the submucosa but a significantly increased accumulation within the muscularis after 1 h SMA occlusion, which was not seen after a more elongated occlusion period. A reperfusion shock without normalization of the serum lactate level and the intramural pHi suggesting intestinal perfusion disturbances may also lead to a depression of the leucocytic accumulation within the muscularis.

[Behavior of the lactate level in occlusion and reperfusion of the right superior mesenteric artery. An animal experiment study]

The value of lactate in the early clinical diagnosis of acute mesenteric arterial occlusion was evaluated in an animal model. The superior mesenteric artery of pigs (8-9 weeks old, 20-23 kg) was clamped for 1 h (group 2, n = 9) and 3 h (group 3, n = 6). Reperfusion was recorded for 2 h. Follow-up measurements were done in six animals (group 1). The systolic blood pressure was elevated significantly to about 18-40 mmHg in the initial phase of ischemia (P = 0.02). The intramucosal pHi measured tonometrically was decreased to below a value of 7.08 (P = 0.03), and the flow of superior mesenteric vein was reduced by about 90% ( P = 0.03) in groups 2 and 3. Within 30 min the lactate increased to about 2.05-3.8 mmol/l in the central venous blood sample and 2.8-4.8 mmol/l in the portal vein blood sample in 30 min. After 3 h of ischemia (group 3) the elevated lactate level returned to normal without any significant difference. In the reperfusion period (group 2) the systolic blood pressure stabilized at a depressed level (63-73 mmHg, P = 0.0054), and the flow of the superior mesenteric vein showed a reduction of 41% (P = 0.03). Intramucosal pHi and lactate values returned nearly completely to normal within 2 h. Reperfusion after 3 h of ischemia (group 3) caused marked shock without any sign of recovery at intramucosal pH or mesenteric vein flow. The lactate values increased for above the ischemic level. In conclusion, an elevated lactate level only correlates with the initial phase of acute mesenteric arterial occlusion. A normal lactate concentration cannot exclude the diagnosis of mesenteric ischemia. Reperfusion of the ischemic intestine is characterized by circulatory shock with secondary increased lactate concentration without predictive value for adequate intestinal perfusion.

High-pressure proton NMR study of lateral self-diffusion of phosphatidylcholines in sonicated unilamellar vesicles

Effects of pressure on the lateral diffusion of phospholipid molecules in sonicated pure 1,2-dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) vesicles (15 wt%) in D2O were examined using the high-pressure proton NMR rotating frame spin-lattice relaxation time (T1rho) method. Proton T1rho were measured at pressures from 1 bar to 5000 bar and at temperatures of 50 degrees C to 70 degrees C for DPPC and 5 degrees C to 35 degrees C for POPC. The T(-1)1rho values were plotted as a function of the square root of the spin-locking field angular frequency (omega1(1/2) and the lateral diffusion coefficient (D) calculated from the slope. Pressure effects on lateral diffusion were observed in the liquid-crystalline (LC) phase. The lateral diffusion coefficient exhibited sharp decreases in response to the various pressure-induced phase transitions encountered. However, pressure had little, if any, effect on lateral diffusion in the pressure-induced gel I (GI) phase and pressure-induced interdigitated gel (Gi) phase. The activation volumes for diffusion were calculated from the slopes from plots of In D versus pressure for both DPPC (37 ml/mol at 50 degrees C, 34 ml/mol at 60 degrees C and 25 ml/mol at 70 degrees C) and POPC (16 ml/mol at 5 degrees C, 9 ml/mol at 20 degrees C and 6 ml/mol at 35 degrees C) sonicated vesicles in the LC phase. The activation energy for diffusion (Ea) was calculated using the slopes from plots of In D versus the inverse of the temperature (1/T) for both DPPC and POPC in the LC phase (3.5 kcal/mol and 3.9 kcal/mol, respectively) and for both DPPC and POPC in the GI phase (6.0 kcal/mol and 4.4 kcal/mol, respectively). From the lateral diffusion coefficient and line width data pressure-temperature phase diagrams for sonicated pure DPPC and POPC vesicles were constructed. The values of the temperature to pressure equivalence of DPPC (dTm/dP) were estimated to be 22.1 degrees C/kbar for the LC to GI phase transition and 28.6 degrees C/kbar for the GI to Gi phase transition. The value of the temperature to pressure equivalence of POPC for the LC to GI phase transition was estimated to be 19.0 degrees C/kbar.

NMR study of the cold, heat, and pressure unfolding of ribonuclease A

The reversible cold, heat, and pressure unfolding of RNase A and RNase A--inhibitor complex were studied by 1D and 2D 1H NMR spectroscopy. The reversible pressure denaturation experiments in the pressure range from 1 bar to 5 kbar were carried out at pH 2.0 and 10 degrees C. The cold denaturation was carried out at 3 kbar, where the protein solution can be cooled down to -25 degrees C without freezing. Including heat denaturation experiments, the experimental data obtained allowed us to construct the pressure--temperature phase diagram of RNase A. The experimental results suggest the possibility that all three denaturation processes (cold, heat, and pressure) lead to non-cooperative unfolding. The appearance of a new histidine resonance in the cold-denatured and pressure-denatured RNase A spectra, compared to the absence of this resonance in the heat-denatured state, indicates that the pressure-denatured and cold-denatured states may contain partially folded structures that are similar to that of the early folding intermediate found in the temperature-jump experiment reported by Blum et al. [Blum, A. D., et al. (1978) J. Mol. Biol. 118, 305]. A hydrogen-exchange experiment was performed to confirm the presence of partially folded structures in the pressure-denatured state. Stable hydrogen-bonded structures protecting the backbone amide hydrogens from solvent exchange were observed in the pressure-denatured state. These experimental results suggest that the pressure-denatured RNase A displays the characteristics of a the inhibitor 3'-UMP show that the RNase A-inhibitor complex is more stable than RNase without the inhibitor.

High pressure 2H-NMR study of the order and dynamics of selectively deuterated dipalmitoyl phosphatidylcholine in multilamellar aqueous dispersions

High pressure 2H multipulse NMR techniques were used to investigate the effects of pressure on the structure and dynamics of selectively deuterated 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) multilamellar aqueous dispersions. The samples were deuterated on both chains at positions 2, 9, or 13. The deuterium lineshapes, the spin-lattice relaxation times, T1, and the spin-spin relaxation times, T2, were measured as a function of pressure from 1 bar to 5 kbar at 50 degrees C for the three deuterated DPPC samples. This pressure range permitted us to explore the phase behavior of DPPC from the liquid-crystalline (LC) phase through various gel phases such as the Gel I (P beta), Gel II (L beta), Gel III, Gel X, and the interdigitated, Gel i, gel phase. Pressure had an ordering effect on all chain segments both in the LC phase and various high pressure gel phases as indicated by the increase in SCD bond order parameter and the first moment, M1, with pressure. Compared with the adjacent gel phases, the Gel i phase had the highest order. Also, in all gel phases the carbon-9 segment of the chains had the most restricted motions in contrast to the LC phase, where the carbon-2 segment was the most restricted. In the LC phase, T1 and T2 values for all segments decreased with pressure, indicative of the fast correlation time regime. Similarly, T1 decreased with pressure in the Gel I and the interdigitated Gel i gel phases but changed to the slow correlation time regime at the Gel i/Gel II phase transition. For T2, which reflects slow motions, the transition to the slow correlation time regime occurred already at LC/Gel I phase transition. Considering the various motions which contribute to relaxation, the behavior of T1 and T2 in the Gel 11 through Gel X phases showing discontinuities and slope changes at the phase transitions was, as expected, quite complex.In addition we found a straight line relationship for T-1 vs. S2D, and T-1 vs. S2CD for the deuterons in the 9 and 13 positions in the LC phase in the pressure range investigated.

One and two dimensional 1H-NMR studies of pressure and tetracaine effects on sonicated phospholipid vesicles

One and two dimensional 1H-NMR experiments have been performed to study the molecular order and dynamics of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) unilamellar vesicles under the influence of high pressure and the local anesthetic, tetracaine (TTC), which can also be considered as a model-charged amphiphile. The TTC molecules have an ordering effect on the headgroups but a disordering effect on the acyl chains, whereas, pressure has an ordering effect on the acyl chains. The results from 2D NOESY experiments on pure DPPC vesicles show that the intensities of NMe3/CH3, NMe3/(CH2)n, and CH3/(CH2)n cross-peaks increase with increasing pressure in the liquid-crystalline phase but decrease with pressure in the gel phase, further suggesting that the appearance of the cross-peaks between the two extremes of the DPPC molecules is due to spin-diffusion. For the DPPC/TTC vesicles, the 2D NOESY experiments confirm that charged TTC molecules are located in the headgroup region of the DPPC bilayers and, in the gel phase, also suggest the formation of an interdigitated gel phase.