Usefulness of saline pushing in reduction of contrast material dose in abdominal CT: evaluation of time–density curve for the aorta, portal vein and liver

The effects of saline pushing after contrast material injection were investigated as well as the possibility for this technique to reduce contrast material doses in liver CT examinations. 52 patients were divided randomly into three groups: 100 ml of contrast material (300 mg I ml(-1)) only (A; n = 19), 100 ml of contrast material pushed with 50 ml of saline solution (B; n = 17), and 85 ml of contrast material pushed with 50 ml of saline solution (C; n = 16). Single-level images were obtained at the level of the main portal vein after the initiation of contrast material injection. There were no significant differences in the mean peak enhancement values (PE) and the mean time to peak enhancement values (TPE) of the aorta between the three groups. The mean PE of the portal vein in group B increased 21 HU over that in group A (p<0.05), and there was no significant difference between groups A and C. The mean PE of the liver in group B increased 7 HU over that in group A (p<0.05), and there was no significant difference between groups A and C. The mean TPE of the portal vein was shorter by 4 s (p<0.05), and that of the liver was shorter by 5 s (p<0.05) in group C compared with those in group A. In conclusion, saline pushing increases the enhancement values of the portal vein and liver, and allows a contrast material dose reduction of 15 ml without decreasing hepatic and vascular enhancement at adequate scan timing.

Spin Triplet Superconducting State due to Broken Inversion Symmetry in Li(2)Pt(3)B

We report (11)B and (195)Pt NMR measurements in noncentrosymmetric superconductor Li(2)Pt(3)B. We find that the spin susceptibility measured by the Knight shift remains unchanged across the superconducting transition temperature T(c). With decreasing temperature (T) below T(c), the spin-lattice relaxation rate 1/T(1) decreases with no coherence peak and is in proportion to T3. These results indicate that the Cooper pair is in the spin-triplet state and that there exist line nodes in the superconducting gap function. They are in sharp contrast to those in the isostructural Li(2)Pd(3)B which is a spin-singlet, s-wave superconductor, and are ascribed to the enhanced spin-orbit coupling due to the lack of spatial inversion symmetry. Our finding points to a new paradigm where exotic superconductivity arises in the absence of electron-electron correlations.

Genetic control of the spontaneous activation of CD4+ Th cells in systemic lupus erythematosus-prone (NZB x NZW) F1 mice

The F(1) hybrid of autoimmune hemolytic anemia-prone NZB and nonautoimmune NZW strains of mice has been studied as a murine model of systemic lupus erythematosus. Both NZB and F(1) hybrid mice show age-dependent spontaneous activation of peripheral CD4(+) T cells as reflected by the elevated frequencies of CD4(+) T cells positive for CD69 early activation marker. Both strains also show age-dependent abnormal decrease of the frequencies of CD62L(+) naive CD4(+) T cells and/or NTA260(+) memory CD4(+) T cells in the spleen. We studied the multigenic control of these abnormal features of peripheral CD4(+) T cells in (NZB x NZW) F(1) x NZW backcross mice by quantitative trait loci mapping and by association rule analysis. The abnormally elevated frequencies of CD69(+)CD4(+) T cells and decreased frequencies of CD62L(+) naive and/or NTA260(+) memory CD4(+) T cells were under the common genetic control, in which the interaction between MHC and a hitherto unknown locus, designated Sta-1 (spontaneous T-cell activation) on chromosome 12, plays a major role. The allelic effects of these loci likely predispose CD4(+) T cells to the loss of self-tolerance, and are responsible for the accelerated autoimmune phenotypes of (NZB x NZW) F(1) hybrid mice.

Virtual CT colectomy by three-dimensional imaging using multidetector-row CT for laparoscopic colorectal surgery

Laparoscopic colorectal surgery has been attracting attention for its capacity to improve the quality of life (QOL) of patients. However, there are disadvantages to this approach, namely, it is difficult to obtain an image of the entire view of the operative field, and organs and lesions cannot be manipulated directly by the surgeon during surgery. For this reason, it takes a relatively large amount of time to ligate vessel, which can vary between patients. Furthermore, vessels and organs can be damaged during lymph nodes dissection under laparoscopic guidance, leading to heavy bleeding that prevents the surgeon from having access to a good view of the operative field. Then, to assess preoperatively the vascular anatomy, we carried out multiphase, contrast-enhanced examinations using multidetector-row CT (MDCT) on patients with colorectal cancer, and prepared the fused image of 3D images of arteries, veins, the colorectum, organs, and tumor. We called the utilization of 3D imaging virtual CT colectomy, which contributed to rapid and safe manipulation of the origins of the arteries and the veins, as well as lymph nodes dissection, without incurring injury to the involved arteries and veins.

Phenylalanine ammonia-lyase modified with polyethylene glycol: potential therapeutic agent for phenylketonuria

Phenylketonuria (PKU) is an autosomal recessive genetic disease caused by the defects in the phenylalanine hydroxylase (PAH) gene. Individuals homozygous for defective PAH alleles show elevated levels of systemic phenylalanine and should be under strict dietary control to reduce the risk of neuronal damage associated with high levels of plasma phenylalanine. Researchers predict that plant phenylalanine ammonia-lyase (PAL), which converts phenylalanine to nontoxic t-cinnamic acid, will be an effective therapeutic enzyme for the treatment of PKU. The problems of this potential enzyme therapy have been the low stability in the circulation and the antigenicity of the plant enzyme. Recombinant PAL originated from parsley (Petroselinum crispum) chemically conjugated with activated PEG2 [2,4-bis(O-methoxypolyethyleneglycol)-6-chloro-s-triazine] showed greatly enhanced stability in the circulation and was effective in reducing the plasma concentration of phenylalanine in the circulation of mice. PEG-PAL conjugate will be an effective therapeutic enzyme for the treatment of PKU.

Perineal-onset Fournier’s gangrene in a patient undergoing hemodialysis – importance of perineal-onset manifestation

We present a rare case of perineal-onset Fournier's gangrene in a patient undergoing hemodialysis. A 51-year-old Japanese man manifested an acute-onset perineal pain with perirectal abscess; subsequently, the pain extended to the abdomen, chest, and loin despite quick treatment. His consciousness deteriorated to delirium and he died of septic shock on the third day of admission. Computed tomography (CT) revealed soft-tissue air along the right rectal wall, moreover, the infection extended to the anterior wall of the bladder and the right peripsoas muscle. On the basis of the clinical course and CT findings, the patient was diagnosed as having the complications of Fournier's gangrene, however, no scrotal lesions were detected. Fournier's gangrene is considered to be easily diagnosed on the basis of skin lesions, such as scrotal erythema and swelling. However, in the early stage, the diagnosis of Fournier's gangrene is difficult in a patient with perineal pain before the detection of skin lesions. In conclusion, definitely the key to improving the prognosis of this fulminant infection is the prompt recognition of the pathological process. Therefore, Fournier's gangrene should always be considered when patients undergoing hemodialysis manifest perirectal disorders, even when no scrotal lesions are detected, because there is the possibility of intra-abdominal and intra-retroperitoneal infections resulting in septic shock.

Soft palate movement during sucking behavior

To clarify the aspects and role of oropharyngeal closure, soft palate movements during sucking were observed and then assessed by electromyographic and fluoroscopic analyses. Three patterns of sucking movements by the palatoglossus and levator veli palatini muscles were analyzed with electromyographic means in seven healthy adults. Furthermore, a forced sucking maneuver, which required special effort to produce a strong sucking pressure by opening the jaw, was analyzed using lateral fluoroscopy in three of the subjects. During all tested sucking movements, the palatoglossus muscle showed continuous activity. The levator veli palatini muscle did not show remarkable activity during regular air sucking or water sucking when water was held in the oral cavity. However, its participation increased when intraoral sucking pressure was increased by opening the jaw, and lateral fluoroscopic examinations revealed that the soft palate was pulled toward the oral cavity to form a tight contact between the rostral portion of the soft palate and the retrotongue, causing the soft palate to make an "L" shape. The palatoglossus muscle plays a major role in palatal movement during sucking. Furthermore, the levator veli palatini muscle, whose activity was observed only during high-pressure sucking with an open jaw, may act to maintain tension in the soft palate against strong negative pressure in the oral cavity.

Binding of KRH-594, an antagonist of the angiotensin II type 1 receptor, to cloned human and rat angiotensin II receptors

We studied the binding properties of KRH-594, a new selective antagonist of angiotensin II (AII) type 1 (AT1) receptors, to rat liver membranes and to recombinant AT1 and AT2 receptors. Preincubation of rat liver membranes with KRH-594 produced maximal inhibition of [125I]-AII binding when the preincubation time was 1-2 h. Preincubation with KRH-594 for 2 h decreased the B(max) value and increased the Kd value. For human AT1, human AT2, rat AT1A and rat AT1B receptors, the Ki values for KRH-594 were 1.24, 9360, 0.67, and 1.02 nm, respectively. The rank order of K1 values for human AT1 receptors was KRH-594 >> EXP3174 > candesartan = AII. The order of specificities for human AT1 and AT2 receptors was candesartan > EXP3174 > KRH-594. Although a 2-h preincubation of human AT2 receptors with KRH-594 (30 microM) or CGP 42112 (a selective AT2 receptor antagonist; 0.3 nM) inhibited binding of [125I]-AII, the suppression by KRH-594 was not significant. These results indicate that KRH-594 binds potently to AT1 receptors in an insurmountable manner, and that at a very high dose (30 microM) it may also bind to AT2 receptors, but in a surmountable manner.

Chymotrypsin modified with polyethylene glycol catalyzes peptide synthesis reaction in benzene

Chymotrypsin was modified in the zymogen form with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine (activated PEG2), followed by activation with trypsin. The modified enzyme was soluble in benzene and retained its enzymic activity. Acid-amide bond formation by the modified enzyme proceeded efficiently in benzene: N-benzoyltyrosine butylamide was made from N-benzoyl-L-tyrosine ethyl ester and n-butylamine, and benzoyltyrosine(oligo)phenylalanine ethyl esters were formed from N-benzoyl-L-tyrosine ethyl ester and L-phenylalanine ethyl ester.

Structural characterization and formation kinetics of sitting-atop (SAT) complexes of some porphyrins with copper(II) ion in aqueous acetonitrile relevant to porphyrin metalation mechanism. Structures of aquacopper(II) and cu(II)-SAT complexes as determined by XAFS spectroscopy

The formation of the sitting-atop (SAT) complexes of 5,10,15,20-tetraphenylporphyrin (H(2)tpp), 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (H(2)t(4-Clp)p), 5,10,15,20-tetramesitylporphyrin (H(2)tmp), and 2,3,7,8,12,13,17,18-octaethylporphyrin (H(2)oep) with the Cu(II) ion was spectrophotometrically confirmed in aqueous acetonitrile (AN), and the formation rates were determined as a function of the water concentration (C(W)). The decrease in the conditional first-order rate constants with the increasing C(W) was reproduced by taking into consideration the contribution of [Cu(H(2)O)(an)(5)](2+) in addition to [Cu(an)(6)](2+) to form the Cu(II)-SAT complexes. The second-order rate constants for the reaction of [Cu(an)(6)](2+) and [Cu(H(2)O)(an)(5)](2+) at 298 K were respectively determined as follows: (4.1 +/- 0.2) x 10(5) and (3.6 +/- 0.2) x 10(4) M(-1) s(-1) for H(2)tpp, (1.15 +/- 0.06) x 10(5) M(-1) s(-1) and negligible for H(2)t(4-Clp)p, and (4.8 +/- 0.3) x 10(3) and (1.3 +/- 0.3) x 10(2) M(-1) s(-1) for H(2)tmp. Since the reaction of H(2)oep was too fast to observe the reaction trace due to the dead time of 2 ms for the present stopped-flow technique, the rate constant was estimated to be greater than 1.5 x 10(6) M(-1) s(-1). According to the structure of the Cu(II)-SAT complexes determined by the fluorescent XAFS measurements, two pyrrolenine nitrogens of the meso-substituted porphyrins (H(2)tpp and H(2)tmp) bind to the Cu(II) ion with a Cu-N(pyr) distance of ca. 2.04 A, while those of the beta-pyrrole-substituted porphyrin (H(2)oep) coordinate with the corresponding bond distance of 1.97 A. The shorter distance of H(2)oep is ascribed to the flexibility of the porphyrin ring, and the much greater rate for the formation of the Cu(II)-SAT complex of H(2)oep than those for the meso-substituted porphyrins is interpreted as due to a small energetic loss at the porphyrin deformation step during the formation of the Cu(II)-SAT complex. The overall formation constants, beta(n), of [Cu(H(2)O)(n)()(an)(6)(-)(n)](2+) for the water addition in aqueous AN were spectrophotometrically determined at 298 K as follows: log(beta(1)/M(-1)) = 1.19 +/- 0.18, log(beta(2)/M(-2)) = 1.86 +/- 0.35, and log(beta(3)/M(-3)) = 2.12 +/- 0.57. The structure parameters around the Cu(II) ion in [Cu(H(2)O)(n)(an)(6-n)](2+) were determined using XAFS spectroscopy.

Clinical application of the reversed pedicled venous flap containing perivenous areolar tissue and/or nerve in the hand

A reversed pedicled venous flap containing perivenous areolar tissue and/or nerve was used to cover traumatic skin defects of seven fingers in six patients. The series consisted of six men, ranging in age from 20 to 57 years (average: 39 years). The reconstructed sites were four dorsal skin defects and three volar skin defects of the finger. The flap was designed on the dorsum of the hand, in such a way as to place a vein at the centre of the flap and not to involve the dorsal metacarpal artery. The flap contained a dorsal vein, perivenous areolar tissue and fascia of the interosseous muscle. Cutaneous nerves were present in three of the seven flaps. The pedicle of the flap was dissected distally to the finger web space and the flap was transferred to the skin defect. The size of the flap ranged from 1.4x4.5 cm to 6.0x7.0 cm. The average length of the pedicle was 1.6 cm. Skin grafting was needed at the donor site in one case (flap size: 6.0x7.0 cm), but primary closure was possible in the remaining cases. Postoperatively, the largest flap showed superficial necrosis, although it survived. The remaining flaps survived completely. This suggests that in a large flap the skin should be attached to the pedicle to prevent congestion. The flap can be elevated without reference to the dorsal metacarpal artery at the ulnar side of the dorsum of the hand. The flap is an effective option to reconstruct skin defects of the finger, especially the little finger.

Glutamate synthesis via photoreduction of NADP+ by photostable chlorophyllide coupled with polyethylene-glycol

Chlorophyllide a was coupled with alpha-(3-aminopropyl)-omega-methoxypoly(oxyethylene) (PEG-NH2) to form a PEG-chlorophyllide conjugate through an acid-amide bond. The conjugate catalyzed the reduction of methylviologen in the presence of 2-mercaptoethanol. It also catalyzed the photoreduction of NADP+ or NAD+ in the presence of ascorbate as an electron donor and ferredoxin-NADP+ reductase as the coupling enzyme. Utilizing the reducing power of NADPH generated by PEG-chlorophyllide conjugate under illumination, glutamate was synthesized from 2-oxoglutarate and NH4+ in the presence of glutamate dehydrogenase. PEG-chlorophyllide conjugate was quite stable toward light illumination compared with chlorophyll a. The increase in the molecular weight of PEG in the PEG-chlorophyllide conjugates was accompanied by the enhancement of photostability of the conjugate and also by the increased solubility in the aqueous solution.

Inhibition of neuronal nitric oxide synthase ameliorates renal hyperfiltration in streptozotocin-induced diabetic rat

Systemic inhibition of nitric oxide synthase (NOS) in streptozotocin-induced (STZ-induced) diabetic rats results in decreases in glomerular filtration rate (GFR) and renal plasma flow (RPF) and an increase in renal vascular resistance (RVR). However, the exact isoform of NOS involved in diabetic renal hyperfiltration has not been determined. This study was conducted to clarify whether NO derived from neuronal NOS is involved in diabetic renal hyperfiltration when using a selective inhibitor of neuronal NOS, 7-nitro indazole (7-NI). Continuous infusion of NG-nitro-L -arginine methyl ester (L-NAME) at 5 microg/kg/min ameliorated renal hyperfiltration, decreased RPF, and increased RVR in diabetic rats without affecting the mean arterial pressure (MAP). 7-NI administered intraperitoneally in diabetic rats significantly reduced GFR without affecting MAP, but the renal hyperfiltration was still observed after the administration of 7-NI. The combined administration of L-NAME after 7-NI caused a further decrease in GFR in diabetic rats and ultimately resulted in normalization of GFR. 7-NI did not change any parameters of renal hemodynamics in control rats. Urinary excretion of nitrite/nitrate and cyclic guanosine monophosphate was significantly increased in diabetic rats over values found in control rats. Our results suggested that a local inhibition of NO in the kidney was involved in the amelioration of diabetic renal hyperfiltration and that NO derived from neuronal NOS is involved, at least in part, in renal hyperfiltration in STZ-induced diabetic rats.

Dynamic study of metal-ion incorporation into porphyrins based on the dynamic characterization of metal ions and on sitting-atop complex formation

We succeeded in the detection of the sitting-atop (SAT) copper(II) complex of TPP (5,10,15,20-tetraphenylporphyrin) in acetonitrile (AN) as a solvent with a very low Brønsted basicity, where two pyrrolenine nitrogens in the Cu(II)-SAT complex coordinate to the metal ion and two protons still remain on the pyrrole nitrogens. The structure parameters around the copper(II) ion in the Cu(II)-SAT complex, as determined by a fluorescent EXAFS method, suggest an axially elongated and equatorially distorted six-coordinate geometry. We measured the rates of the formation reaction of the SAT complexes for a series of transition metal(II) ions in AN using the stopped-flow technique. We propose the mechanism where there is a rapid deformation equilibrium of the porphyrin ring prior to the rate-determining step of the bond rupture of a coordinated solvent molecule on the metal(II) ion. Furthermore, we measured the rates of the deprotonation reaction of the Cu(II)-SAT complex by some Brønsted bases and indicated that the rate-determining step is the attack of the base on the proton of the pyrrole nitrogen in the SAT complex. Finally, a unified mechanism relevant to the porphyrin metalation mechanism has been proposed.

Effects of dopamine d2 receptor agonists in a pituitary transplantation-induced hyperprolactinaemia/anovulation model in rats

1. In the present study, we investigated the effects of hyperprolactinaemia, induced by transplantation of anterior pituitary glands under the kidney capsule in female rats, on the relationship between serum and pituitary concentrations of the gonadotropins and on the oestrous cycle. 2. Rats with pituitary transplants showed increased serum prolactin concentrations and decreased serum concentrations of gonadotropins and increased pituitary concentrations of gonadotropins. Moreover, these rats showed persistent dioestrous and anovulation from 3 to 6 days after transplantation. 3. A single oral administration of cabergoline (at doses between 0.001 and 0.1 mg/kg) dose-dependently inhibited the elevated serum prolactin concentrations in hyperprolactinaemic rats. At 0.1 mg/kg, cabergoline induced a continuous reduction in serum prolactin concentrations for 5 days after administration. Terguride (0.1 mg/kg) and bromocriptine (10 mg/kg) also reduced serum prolactin concentrations at 1 and 3 days after administration. All three dopamine D2 receptor agonists increased serum gonadotropin concentrations and ovarian weight at 3 days after administration. 4. In rats exhibiting anovulation, a single oral administration of any one of the three dopamine D2 receptor agonists dose-dependently restored ovulation and a normal oestrous cycle appeared. Oral administration of cabergoline (0.03 mg/kg) or terguride (0.1 mg/kg) restored ovarian function and abolished the anovulation following a reduction in serum prolactin concentrations. However, bromocriptine (10 mg/kg) did not completely abolish anovulation. Following administration of terguride (0.3 mg/kg) or bromocriptine (30 mg/kg), only one normal oestrous cycle appeared; however, following cabergoline (0.1 mg/kg), two normal oestrous cycles appeared. 5. These results suggest that cabergoline has a potent and long-lasting action as a dopamine D2 receptor agonist and, thus, should be a useful drug for the treatment of galactorrhoea and hyperprolactinaemic amenorrhoea and/or anovulation in humans.

DXAFS study on the decarbonylation process of Mo(CO)6 in NaY supercages

The decarbonylation process of Mo(CO)6 in the NaY supercages was studied by means of a time resolved dispersive XAFS method during temperature programmed decarbonylation. XANES analysis demonstrated that the decarbonylation proceeded through two steps and that a stable intermediate existed between 440-490 K. The curve fitting analysis revealed that the intermediate was a molybdenum monomer subcarbonyl species coordinated by three CO ligands and three oxygen atoms of zeolite framework. Molybdenum dimer subcarbonyl species were not observed. This study demonstrated that DXAFS technique is a powerful method to study the dynamic behaviour of the Mo carbonyl species during decarbonylation process.

Time-resolved energy-dispersive XAFS study on the reduction process of Cu-ZSM-5 catalysts

The time-resolved reduction process of copper cations in ZSM-5 during temperature-programmed reduction (300-700 K) was studied by energy dispersive X-ray absorption fine structure (DXAFS). The Cu K-edge DXAFS spectra for isolated Cu2+ species in the channels of ZSM-5 were recorded at an interval of 1 s during the reduction. The curve fitting analysis of the EXAFS data and the XANES analysis revealed that the isolated Cu2+ species in the channels were reduced stepwise. They were reduced to isolated Cu+ species at 400-450 K and the Cu+ species to Cu0 metallic clusters at 550-650 K. Small clusters like Cu4 were initially formed, followed by particle growth. A small part of them went out to the outer surfaces of ZSM-5 during the reduction.

KRH-594, a new angiotensin AT1 receptor antagonist, prevents end-organ damage in stroke-prone spontaneously hypertensive/Izm rats

1. In the present study, we examined whether KRH-594, a new angiotensin AT1 receptor antagonist, would stop the progression of renal failure and end-organ damage and improve the survival rate in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP/Izm). 2. Oral administration of KRH-594 (3 and 10 mg/kg per day) for 11 weeks significantly reduced systolic blood pressure, urinary total protein, blood urea nitrogen, serum creatinine and urinary N-acetyl glucosaminidase and increased creatinine clearance in SHRSP/Izm. 3. In a histological study, KRH-594 (3 and 10 mg/kg per day) significantly improved the glomerulosclerosis, basophilic change and hyalin cast of tubules, proliferation of afferent arterioles and interlobular artery wall scores of the kidney and the cardiac fibrosis scores of the heart in SHRSP/Izm. KRH-594 (3 and 10 mg/kg per day) also significantly inhibited cardiac hypertrophy. 4. KRH-594 (3 and 10 mg/kg per day) prevented death in SHRSP/Izm during the examination period. 5. These results suggest that KRH-594 improves hypertensive complications, such as renal failure, cardiac hypertrophy and thickening of the artery wall, and prevents death in salt-loaded SHRSP/Izm.

Immune tolerance induced by polyethylene glycol-conjugate of protein antigen: clonal deletion of antigen-specific Th-cells in the thymus

Polyethylene glycol (PEG) conjugates of protein antigens induce antigen-specific immune tolerance of helper T (Th)-cells. However, the mechanism of this Th-cell tolerance has remained unelucidated. Using transgenic mice with ovalbumin (OVA)-specific T-cell receptor (TCR) genes, we examined the response of OVA-specific Th-cells towards tolerogenic PEG-conjugate of OVA in vitro and in vivo. When stimulated with PEG--OVA in vitro, transgenic OVA-specific Th-cells proliferated and produced interleukin 2, the levels of which were comparable to those induced by unmodified OVA. In contrast, PEG--OVA administered into the circulation of transgenic mice induced unresponsiveness in peripheral OVA-specific Th-cells. Moreover, in the thymus of these transgenic mice, the frequency of immature CD4+CD8+ (double positive) thymocytes was reduced. A similar phenomenon was not observed in transgenic mice treated with unmodified OVA. As autoreactive T-cells are known to be clonally deleted at the immature double positive stage in the thymus. Th-cell tolerance induced by PEG--protein antigens is at least in part mediated by central tolerance in the thymus, and is likely caused by the markedly enhanced stability of PEG--protein conjugates in the circulatory system.

Innervated radial thenar flap combined with radial forearm flap transfer for thumb reconstruction

A radial thenar flap combined with radial forearm flap was used for the reconstruction of the ipsilateral thumb in four patients. Vascular supply of the combined flap was based on the radial artery and extending the vascular pedicle to the superficial palmar branch of the radial artery. The flap was sensated by the palmar branch of the superficial radial nerve. The size of the flap averaged 15 x 5 cm and the innervated region of the thenar eminence was an area approximately 5 x 3 cm located over the proximal parts of the abductor pollicis brevis and opponens pollicis muscles. The flap was transferred as a free flap in three patients and as an advancement flap in one patient. The flaps survived completely without complications. Satisfactory restoration of sensation was achieved in the flap area, as shown by 6 mm of average moving two-point discrimination. This combined flap may be a feasible reconstructive option for large palmar defects of the fingers such as degloving injuries.

Spectrophotometric analysis of 5-coordinate cobalt(II) species for ligand substitution of hexakis(acetonitrile)cobalt(II) with bulky 1,1,3,3-tetramethylurea in noncoordinating nitromethane

The ligand substitution reaction of [Co(an)6]2+ (an = acetonitrile) with 1,1,3,3-tetramethylurea (TMU) in the noncoordinating solvent, nitromethane, was spectrophotometrically investigated by titration. The observed spectral changes were analyzed using a model with the four steps of ligand substitution. The component complexes involved in the substitution were found to be 6-coordinate [Co(an)6]2+ and [Co(an)5(tmu)]2+, 5-coordinate [Co(an)3(tmu)2]2+ and [Co(an)2(tmu)3]2+, and 4-coordinate [Co(tmu)4]2+. The logarithmic values of the stepwise equilibrium constant are 2.17 +/- 0.26, 1.06 +/- 0.15, 1.19 +/- 0.06, and -0.4 +/- 0.4 at 25 degrees C. The decrease in the coordination number of the Co(II) ion from 6 to 5 during the formation of [Co(an)3(tmu)2]2+ and from 5 to 4 during the formation of [Co(tmu)4]2+ is ascribed to the steric repulsion between the coordinating bulky TMU molecules.