Ultrafast spectroscopy of RuII polypyridine complexes in the gas phase and the liquid phase: [Ru(2,2'-bipyridine)2(nicotinamide)2]2

[Ru(bipyridine)₂(nicotinamide)₂]²⁺ (1) and its monoaqua-complex [Ru(bipyridine)₂(nicotinamide)(H₂O)]²⁺ (2) were spectroscopically studied for the first time in the gas phase by static and time resolved UV photodissociation spectroscopy, observing nicotinamide and H₂O ligand dissociation for 1 and 2, respectively. Both processes and their ultrafast dynamics were investigated in parallel by transient absorption spectroscopy in aqueous solution. The latter data were newly acquired for the long-wavelength MLCT band excitation of 1 and provide novel ultrafast ligand dissociation results for 2, confirming the gas phase results, i.e., exclusive H₂O cleavage over nicotinamide loss. Similar apparent time constants in the sub-ps and few ps ranges were obtained for 1 in both phases, whereas a larger time constant of ca. two hundreds of ps for the ground state recovery was observed exclusively in the solution phase. Our reaction scheme accounts for faster dissociation dynamics in the gas phase by energetical lowering of the ³MC vs. the ³MLCT states by lack of solvent stabilization of the latter. Based on the apparent time constants, we favour, for the solution dynamics, a fast bimodal vibrational deactivation in the ³MLCT/³MC manifolds and a slow dissociation obfuscated by the ground state recovery. This is substantiated by a similar reaction scheme proposed for the ultrafast dynamics of 2, resulting in a new assignment for transient absorption features with λ > 550 nm to the ³MC manifold, and a common kinetic description for 1 and 2. Computations at the TD-DFT/cc-PVTZ/MDF28 level support our spectroscopic findings and the suggested deactivation pathways.

Photophysical dynamics of a binuclear Cu(i)-emitter on the fs to μs timescale, in solid phase and in solution

Understanding subtle aspects of photophysical behavior is the key to design and synthesize new and improved luminescent materials. We contribute to this with an in-depth photophysical characterization of the binuclear copper complex Cu(i)-NHetPHOS-tris-m-tolylphosphine (1), a member of a recently established emitter class for ultra-efficient, printed organic light-emitting diodes (OLEDs). To this end we studied 1 in solution and in solid form, i.e. neat film and KBr-pellet, by means of femtosecond time-resolved transient absorption/reflectivity, time-correlated single photon counting (TCSPC), and nanosecond time-resolved step-scan FTIR spectroscopy. Using these methods, we explore the photoinduced dynamics from ultrafast Franck-Condon state deactivation until the decay of the luminescent states. Upon photoexcitation, we observed multiexponential dynamics in both solution (e.g. acetonitrile 0.8 ps, 59 ps, 3 ns, 11-13 ns) and in solid state (e.g. neat film 0.3 ps, 35 ps, 670 ps, 0.5-1 μs, 3.5-4.5 μs) with four to five time-constants that significantly depend on the type of sample. Quantum chemical calculations at the DFT level in combination with step-scan vibrational spectroscopy provided structural information about the electronic ground state S₀ and the lowest lying excited state T₁, and show that the latter is populated within 1 μs after photoexcitation. We found thermally activated delayed fluorescence (TADF) for this complex, which has been suggested to be the cause for its high efficiency in printed OLED devices. The results suggest that non-radiative processes, lowering the luminescence quantum yield in solution, are active on the ns to μs timescale.

Age-dependent physiological dynamics in acid-base balance, electrolytes, and blood metabolites in growing goats

There is a paucity of published data reporting acid-base equilibrium in goats, and no information is available on how the acid-base complexity changes when suckling goat kids become ruminants. The aims of this study were to evaluate young healthy goats for age-related changes in serum proteins, metabolites, and electrolytes; differences in results when the Henderson-Hasselbalch equation or strong ion approaches were used were also assessed. To assess biological variability and reproducibility, two consecutive long-term studies, each lasting from the 6th to 56th week of life (wl), were performed in 15 (Study 1) and 10 (Study 2) animals. Blood gas analysis, serum biochemical analysis, and electrophoresis were performed on venous blood, and acid-base information was obtained using the traditional Henderson-Hasselbalch approach, Stewart's strong ion model, and Constable's simplified strong ion model. In all goats within the first 4-5 months, serum concentrations of glucose, l-lactate, and inorganic phosphate decreased significantly, while serum concentrations of total protein, albumin, and gamma globulin increased. Consequently, nonvolatile weak acids (A_{tot Alb} and A_{tot TP}) increased. At the end of this 'adaptation period', i.e. when milk was replaced by purely plant-based food, significantly lower bicarbonate and base excess values were accompanied by blood pH that shifted towards acidosis. Electrolytes (Na⁺, K⁺, Ca²⁺, and Cl^-), anion gap, strong ion difference, and strong ion gap did not show age-dependent trends. In conclusion, somatic growth and development of gastro-intestinal fermentation in growing goats act as complex sources of physiological variability on acid-base equilibrium that was not reflected by the Henderson-Hasselbalch equation only.

Ultrafast excited-state relaxation of a binuclear Ag(i) phosphine complex in gas phase and solution

The [Ag₂(dcpm)₂]²⁺ phosphine complex displays multiexponential excited-state relaxation dynamics both in the gas phase and in solution.

Effect of Parachlamydia acanthamoebae on pulmonary function parameters in a bovine respiratory model

The aim of this study was to evaluate pulmonary dysfunction induced by experimental infection with Parachlamydia acanthamoebae in calves. Intrabronchial inoculation with P. acanthamoebae was performed in 31 calves aged 2-3 months old at two different challenge doses of 10(8) and 10(10) inclusion-forming units (IFU) per animal. Control animals received heat inactivated bacteria. The effects on pulmonary gas exchange were determined by arterial blood gas analysis and haemoximetry during the 7 days post inoculation (DPI). For pulmonary function testing (PFT), impulse oscillometry, capnography, and measurement of O2 uptake were undertaken in spontaneously breathing animals 7 and 3 days before inoculation and were repeated until 10 DPI. In the early phase after challenge (1-3 DPI), mild hypoxaemia occurred, which was accompanied by a significant reduction in both tidal and alveolar volumes (each related to bodyweight, BW). In parallel, expiratory flow rate and specific ventilation (i.e. minute ventilation related to O2 uptake) were significantly increased. Minute and alveolar ventilations (each related to metabolic BW) increased significantly due to higher respiratory rates, lasting until 4 and 5 DPI, respectively. Oxygen uptake was slightly reduced during the first 2 days after challenge, but increased significantly during the recovery phase, from 4 to 8 DPI. No deterioration in respiratory mechanics or acid-base balance was observed. Respiratory infection with 10(10) IFU P. acanthamoebae per calf induced mild respiratory dysfunction, mainly characterised by hypoxaemia. The study's findings do not indicate severe pathophysiological consequences of P. acanthamoebae infection on pulmonary function in the bovine host.

Time-resolved IR spectroscopy of a trinuclear palladium complex in solution

Time-resolved IR spectroscopic methods covering the femto- to microsecond range in combination with (TD-)DFT computations were used to investigate the electronically excited state structure of a trinuclear Pd complex.

Combined theoretical and experimental study of spin and charge dynamics on the homodinuclear complex [Ni2(II)(L-N4Me2)(emb)]

We present a combined theoretical and experimental study of spin and charge dynamics on the homodinuclear compound [Ni2(II)(L-N4Me2)(emb)]. The theoretically calculated oscillator strengths of the ground-state absorption spectrum show an acceptable agreement with experiment. We predict a local ultrafast laser-induced spin-flip scenario, which involves charge-transfer states. Experimentally, we observe charge dynamics on two different time scales. The two relevant, transient electronic states and their electronic properties are also theoretically characterized. These results provide a joint investigation of the homodinuclear complex and suggest a realistic scenario for ultrafast spin dynamics and other optical-related manipulations.

Treatment options and outcome for renal cell tumors in the transplanted kidney

The diagnosis of renal cell carcinoma in a transplanted kidney is rare but with possibly devastating consequences. In addition to transplant nephrectomy, which inevitably results in a return to dialysis, various treatment options such as different techniques for nephron sparing surgery and local ablative procedures (like radiofrequency ablation or cryoablation) have been described in the literature. An important issue is to find the balance between the preservation of the transplant function, on the one hand, which is dependent on the maintenance of an immunosuppressive regimen, and a sufficiently radical tumor therapy on the other hand. To provide an overview of current therapeutic attempts to cure transplant renal cell carcinoma under these conditions, published data on related therapies and outcomes are summarized.

Interventional stenting for ruptured iliac aneurysm following transplant nephrectomy

Surgical removal of a failed kidney graft may lead to a variety of postoperative complications, development of an aneurysm being a relatively rare complication. We report the case of a 34-year-old man who developed an iliac aneurysm 13 years after transplant nephrectomy. Interventional stenting was performed upon the rupture of the aneurysm. Postintervention the function of the contralateral transplanted kidney was stable and the patient recovered. An endoleak was diagnosed after 1 week, which was also stented. No operative procedure was necessary. In conclusion, even in an emergency situation interventional stenting of a false iliac aneurysm after transplant nephrectomy may be a therapeutic option.

Recurrent Complicated Colon Diverticulitis in Renal Transplanted Patient

Colon perforation due to diverticulitis is a life-threatening complication in the postoperative course of kidney transplantation. In the immunocompromised patient a diagnosis of diverticulitis is difficult to make. We report a 53-year-old woman being kidney transplanted 14 years ago with known diverticulosis. She was admitted with acute severe pain in the lower left abdomen. Abdominal computed tomography (CT) scan indicated a diagnosis of intestinal abscess in the small pelvis. Laparotomy showed a covered sigma perforation with abscess located in the small pelvis (Hinchey-I). Because of the immunocompromised situation of the patient we performed a Hartmann procedure. Her postoperative course was uneventful. In a 6-month interval the intestinal continuity restoration was performed. Twelve days after discharge the patient was readmitted with reduced renal function and increased infection parameters. During physical examination the abdomen was tender. The patient complained of abdominal pain in the left upper abdomen and additional pain in the left shoulder. An antibiotic therapy using ciprofloxacin was already initiated owing to a urinary tract infection. An abdominal CT scan was performed and indicated an intestinal abscess in the left upper abdomen. Laparotomy showed an abscess involving transverse colon, distal jejunum, and proximal ileum (Hinchey-II). Segmental resection of the left colonic flexure, proximal jejunum, and ileum was performed. The postoperative course was uneventful and the patient was discharged on the 8th postoperative day. The present casuistry emphasizes that the immunocompromised patient can undergo diverticulitis twice, and that primary anastomosis is a feasible option for patients with localized peritonitis due to complicated diverticulitis.

Kidney Transplantation Using Donors With History of Diabetes and Hypertension

PURPOSE

Due to the persistant organ shortage for kidney transplantation, donor selection has changed in the past years. Although hypertension and diabetes mellitus are known to be risk factors for renal insufficiency, kidneys from donors with these diagnoses in their history have been accepted for kidney transplantation even with an increased risk of poor graft function. Herein we have reported our experience with kidney transplantation using grafts from donors with both, a history of type II diabetes and hypertension.

METHODS

Between 2000 and 2005, ten patients were grafted using donors with history of type II diabetes mellitus and hypertension. Mean donor age was 58 +/- 7.5 years and recipient age, 52.2 +/- 15.7 years. Mean HLA mismatch was 0.8 (A); 1.2 (B) and 0.9 (DR). Cold ischemia time was 17.4 +/- 4.1 hours. Immunosuppression was based on CyA (n = 7), tacrolimus (n = 2) or sirolimus (n = 1).

RESULTS

Six patients (60%) showed good initial function, and four (40%) had delayed graft function (DGF). One patient died at ten weeks due to multiorgan failure. Two (20%) biopsy-proven rejections were diagnosed, one of which was resistant to therapy. Six months after kidney transplantation, 7 (77%, n = 9) showed good graft function (creatinine 1.3 to 2.4 mg/dL), but one patient displayed long-lasting DGF with poor function.

CONCLUSION

Grafts from donors with a history of diabetes mellitus and hypertension are suitable for kidney transplantation. Elevated rate of DGF (40%) would justify allocation of these organs to local transplant centers to shorten ischemia time and thereby reduce DGF and achieve better long-term results. Identification and detailed evaluation of these donors prior to allocation (eg, HbAlc, biopsy) may help transplant centers to accept these kidneys.

Development of a cell culture assay for the quantitative determination of vaccination-induced antibodies in rabbit sera against Clostridium perfringens epsilon toxin and Clostridium novyi alpha toxin

Cell culture assays are possible alternatives to replace in vivo neutralization tests currently required for potency testing of clostridial vaccines. Cell culture assays based on the MDCK cell line and the Vero cell line which are sensitive to the Clostridium (C.) perfringens type D epsilon toxin and Clostridium novyi type B alpha toxin, respectively, were developed, and the test conditions were standardized. The antibody titres of vaccinated rabbits measured in vitro were compared with the results of current test procedures recommended by European Pharmacopoeia. The correlation coefficients calculated were significant for all sera tested. The cell culture assays proved to be sensitive, specific, reproducible and reliable. Therefore, these cell culture assays could be suitable in vitro alternatives to the in vivo mouse neutralization experiments required for potency tests of clostridial vaccines, but further validation studies are necessary.

Isolation, identification and characterization of group A rotavirus from a chicken: the inner capsid protein sequence shows only a distant phylogenetic relationship to most other avian group A rotaviruses

Rotavirus particles were identified in the intestinal content of a 35-day-old stunted chicken. The virus was isolated, RNA pattern was analysed and the viral genome segment 6 was sequenced. In particular, the sequence data showed a very close similarity to the chicken rotavirus isolate Ch-1 (99.2% amino acid homology), this is distantly related to all known avian rotaviruses and supports the existence of different VP6 types amongst avian group A rotaviruses.

Therapy and Prognosis of Tumors of the Genitourinary Tract After Kidney Transplantation

There is an increased incidence of tumors of the genitourinary tract among kidney graft recipients. From 1979 to 2001, all patients who received kidney transplants had records of both their underlying diseases and their initial immunosuppression. Patients who developed a genitourinary tract malignancy were evaluated for tumor type, location, stage, tumor therapy and clinical course. During this period, 1804 patients underwent 2068 kidney transplantations. Thirty-four patients had 39 tumors of genitourinary origin. One patient was lost to follow-up. There were 15 patients with 18 renal cell carcinomas (one of them multifocal): six had seven transitional cell carcinomas; six, prostatic carcinoma; six, tumor of the female genital tract (one also had a renal cell carcinoma); and two, a seminoma. Most tumors were diagnosed in their early stages (< or = pT3, N0, M0; n = 31 tumors) and thus accessible to curative therapy, achieving good long-term results: 1- and 5-year survival rates of 100% and 91%, which were better than those obtained in advanced stages (N+, M+; n = 7 tumors), namely both 1- and 5-year survival rates of 38% (P < .05). Death was caused by tumor growth in nine patients (27%) and by other causes in three patients (9%). With appropriate treatment genitourinary tumors at early stage show a good prognosis. New immunosuppressants with supposed antiproliferative effects may help to decrease the incidence of malignancies. The most important factor is risk-adapted screening to identify malignancies early and to initiate appropriate therapy.

Evidence of infection in tortoises by Chlamydia-like organisms that are genetically distinct from known Chlamydiaceae species

Nasal lavage fluid was collected from 155 tortoises, mostly Testudo spp., that were kept as companion animals and suffered from nasal discharge. Examination for chlamydial DNA by PCR assays targeting the ompA, ompB, and groESL genes, as well as the 16S rRNA signature region and the 16S-23S intergenic spacer, respectively, revealed 16 (10.3%) positive animals. Sequence analysis of PCR products indicated high homology to the family Chlamydiaceae. Phylogenetic trees constructed from partial sequences of the ompA and 16S rRNA genes showed that the present samples clustered outside the nine species of Chlamydia and Chlamydophila. Sequences of the nearest relative, Chlamydophila pecorum, were still clearly distinct from those of the positive tortoise samples. This suggests that the tortoises had been infected by Chlamydia-like agents, the taxonomic identity and pathogenic importance of which has yet to be established.

Stent migration necessitating surgical intervention

BACKGROUND

Internal drainage with transhepatically or endoscopically placed endoprostheses has been used for many years as a temporary or definitive treatment for biliary tract obstruction. As a late complication, stent migration may occur.

METHODS

We reviewed our records to identify patients who were operated on for a migrated endoprosthesis that was causing complications. In all, five such patients were identified.

RESULTS

One patient had a large bowel perforation. Bowel penetration led to an interenteric fistula in one patient and to a biliocolic fistula formation in another. Small bowel distension was found in two patients. Surgical treatment consisted of local excision in three patients, segmental resection in one patient, and a bypass operation in the patient with biliocolic fistula. Postoperatively, four patients recovered without problems, but one patient died during a complicated postoperative course.

CONCLUSION

If a stent becomes stuck in the gastrointestinal tract and is not accessible for endoscopic removal, early operative revision is mandatory to prevent further complications.

Stent migration necessitating surgical intervention

BACKGROUND

Internal drainage with transhepatically or endoscopically placed endoprostheses has been used for many years as a temporary or definitive treatment for biliary tract obstruction. As a late complication, stent migration may occur.

METHODS

We reviewed our records to identify patients who were operated on for a migrated endoprosthesis that was causing complications. In all, five such patients were identified.

RESULTS

One patient had a large bowel perforation. Bowel penetration led to an interenteric fistula in one patient and to a biliocolic fistula formation in another. Small bowel distension was found in two patients. Surgical treatment consisted of local excision in three patients, segmental resection in one patient, and a bypass operation in the patient with biliocolic fistula. Postoperatively, four patients recovered without problems, but one patient died during a complicated postoperative course.

CONCLUSION

If a stent becomes stuck in the gastrointestinal tract and is not accessible for endoscopic removal, early operative revision is mandatory to prevent further complications.

Influences of naturally occurring and experimentally induced porcine pneumonia on blood parameters

It had been the objective of the studies described to establish local and systemic changes by naturally occurring pneumonia or pneumonia experimentally induced by Pasteurella multocida and Haemophilus parasuis in swine. Acute and chronic pneumonia was found to alter the cytokine level of lung lavage fluid and affect the composition and function of blood cells, especially with regard to phagocytosis, radical formation and cell surface receptors. Interleukin-6 levels in blood plasma rose 24h after experimental intrabronchial infection. The influences of the changes on growth and meat quality are discussed.

[The influence of viscosity on adhesion and invasion of Salmonella strains in an in vitro model]

The influence of viscosity on the adhesion and invasion behaviour of Salmonella strains of different origin was investigated using an in-vitro-model. These processes seem to be strain-dependent. Compared to the controls, the number of internalized Salmonella was elevated. This increase was a result of the greater number of Salmonella which adhered to Caco-2-cells and was detected only for strains from organs of calves having died from salmonellosis. The average motility of these strains was determined to be 1.6 +/- 0.5 mm/h. A possible association between adhesion ability and motility was discussed.

[Development of in vitro methods for the potency testing of clostridial vaccines]

Cell culture assays, using the MDCK cell line was confirmed as being sensitive to the C. perfringens epsilon toxin and VERO cell line to the C. novyi type B alpha toxin. Cell culture assays using these cells were developed and the test conditions were standardised. The antitoxin titres of rabbit antisera were calculated and compared with those of the manufacturers. The correlation coefficients between in vitro and in vivo method were calculated and were significant. The cell culture assay offers a valid in vitro alternative to the animal experiments for the titration of sera generated in the course of potency tests of clostridial vaccines.

Antibody reactions after aerogenous or subcutaneous immunization of pigs with Pasteurella multocida antigens

Depending upon the antigens used and the initial titres, subcutaneous immunization of weaner pigs by means of a temperature-sensitive mutant of live Pasteurella multocida (serovar A), resulted in a significant rise of the level of specific IgG antibody already present in blood serum, but not in lung lavage fluid, and a specific stimulation of lung clearance as compared to non-immunized controls. Aerogenous immunization of a total of 108 animals in 18 experiments did not influence serum antibody titres but produced a significant rise in lung antibodies and P. multocida clearance as compared to an identical number of controls. In all 12 immunization experiments using the live mutant, increased specific IgA antibodies and in seven out of 10 experiments, elevated IgG antibodies were measured. Only aerogenous immunization was found to be capable of reducing the severity of pneumonia induced by intrabronchial infection.

Organ preservation with EC, HTK, and UW, solution in orthotopic rat liver transplantation. Part II. Morphological study

The quality of organ preservation is of major importance in minimizing the incidence of primary graft nonfunction and organ rejection. For this study a new semiquantitative score was developed that grades morphologic tissue alterations in the liver according to their frequency and severity. It was applied to assess commonly used perfusion solutions for their efficacy in preventing early and late tissue damage after rat liver transplantation. For transplantation the livers were stored in Euro-Collins (EC, group I; n = 11), histidine-tryptophan-alpha-ketoglutarate (HTK, group II; n = 11), or University of Wisconsin solution (UW, group III; n = 11). Rat liver transplantation was performed with graft arterialization by the method of Engemann. Biopsies were taken for morphological examination and semiquantitative scoring during the donor operation, after 4 h of cold storage, 1 h after reperfusion, and 4 weeks postoperatively. An immunohistological bromodeoxyuridine (BrdU) assay was also performed on the day of dissection to assess the rate of hepatic proliferation. Semiquantitative morphological analysis gave widely differing results in all experimental groups after 4 h of ischemia. There was less intracellular and interstitial edema, fatty degeneration, intralobular necrosis, and hepatocellular proliferation in the HTK group than in the other groups. Neither after cold ischemia nor 1 h after reperfusion did Kupffer-cell activation occur; this is known to play a major role in the development ofischemia and reperfusion injury. Furthermore, late changes such as bile-duct proliferation and vascular and sinusoidal alterations appeared less frequently in this group. The hepato-protective powers of HTK solution might therefore be due to decreased Kupffer-cell activation.

[Value of electrotherapy within the scope of conservative treatment of anorectal incontinence]

The following study reports on transanal electric stimulation as a conservative method of treatment in anal incontinence. In the centre of interest are clinical examinations on 45 patients that underwent a combined treatment with the IT-system 100 from Reha-Medi and pelvic floor training. A collective of 29 patients only treated with pelvic floor training was used as a control group. The results were based on a thorough medical history ascertainment and the corresponding clinical examinations at the beginning and end of the treatment. Our findings were classified according to the modified score of incontinence of Holschneider [16]. After therapy 42.2% of patients with electric stimulation therapy and 27.6% of the control group showed continence. 40 respectively 62.1% were non responder without relevant benefit. In the electric stimulation group the median score before and after therapy amounted to 6.57 versus 9.24 points. The control group achieved 6.72 respectively 8.58 points. The differences are statistically significant (p < 0.05, Student t-test). Concerning the results in relation to the cause of the incontinence, no significant differences between idiopathic and traumatic origin of the insufficiency of the sphincter mechanism are found in both groups. Therefore all variations of anorectal incontinence are seen as indication for treatment. The international literature as well as our own results confirm that electric stimulation is effective and may be in special cases a major factor in the conservative treatment of anorectal incontinence.

Orthotopic rat liver transplantation and bile duct reconstruction by a splint technique

The aim of the present study is to investigate the impact of bile duct reconstruction by a splint technique, a method which has not been sufficiently researched in animals after liver transplantation. Three experimental groups were set up: I = control, sham operation; II = bile duct reconstruction; III = orthotopic rat liver transplantation (ORLT). After bile duct reconstruction, serum levels of ASAT and ALAT in group II revealed a peak on the first postoperative day. The transplanted animals (group III) showed a second peak in liver enzyme levels on the fifth postoperative day; it was significantly higher than in group II. Serum bilirubin was more elevated in the transplant group, with a peak on day 7. Morphological investigations at the end of surgery revealed only intralobular necrosis and reactive changes in the liver capsule (group II); after transplantation (group III), there was also interstitial and intracellular edema, fatty degeneration and disintegration of the sinusoidal lining. One month later, necrosis, bile duct proliferation, cholestasis, cholangitis and vascular alterations were found in groups II and III. Furthermore, an increased rate of hepatocellular and bile duct proliferation was observed. These findings are partly due to the bile duct reconstruction. We recommend that a bile duct reconstruction control group should be included in ORLT experiments.

Resonance Raman and optical transient studies on the light-induced proton pump of bacteriorhodopsin reveal parallel photocycles

The photocycle of bacteriorhodopsin (bR) was studied at ambient temperature in aqueous suspensions of purple membranes using time-resolved resonance Raman (RR) and optical transient spectroscopy (OTS). The samples were photolyzed, and the fractional concentrations of the retinylidene chromophore in its parent state, BR570, and in the intermediate states L550, M412, N560, and O640 were determined in the time domain 20 microseconds-1 s and in the pH range 4-10.5. Two kinetically different L components could be identified. At pH 7 one fraction of L (approximately 65%) decays in 80 microseconds to M (deprotonation of the Schiff base), whereas the residual part is converted in approximately 0.5 ms to N. The RR spectra reveal only minor structural changes of the chromophore in the L-->N transition. These were attributed to a conformational change of the protein backbone [Ormos, P., Chu, K., & Mourant, J. (1992) Biochemistry 31, 6933]. With decreasing pH the L-->N transition is delayed to > 2 ms following a titration-like function with pKa approximately 6.2. The decay of M412 monitored by OTS can be fitted for each pH value by two different amplitudes and time constants (Mf, tau f; Ms, tau s; f = fast, s = slow). Both Mf and Ms consist of subcomponents which can be distinguished by their different reaction pathways (but not by OTS). Mf occurs in the reaction sequences L-->Mf-->N-->BR and L-->Mf-->O-->BR. The population of the first sequence, in which N is formed with the time constant tau f (approximately 2-4 ms, pH 6-10.5), increases with pH. Ms is also found in two different reaction sequences of the form L-->Ms-->BR. The quantitative analysis reveals that each "titration effect" can be related to a certain fraction of bR. It is proposed that each fraction can be identified with a "subspecies" of bR which undergoes an independent and individual cyclic reaction. A complete reaction scheme is set up which represents the manifold of observed phenomena. It is concluded from the pH dependence of the lifetimes of Ms and N that the reconstitution of BR570 in the reaction steps Ms-->BR and N-->BR requires the uptake of a proton from the external phase. It is argued that this proton catalyzes the reisomerization of retinal, whereas the Schiff base is internally reprotonated from Asp-85. A model for proton pumping is proposed in which the proton taken up from the external phase to catalyze the reisomerization of retinal is the one which is pumped through the membrane during the photocycle of bR.

Picosecond infrared studies of the dynamics of the photosynthetic reaction center

The changes in the vibrational transitions of the protein and redox cofactors of the photosynthetic reaction center were examined by picosecond infrared spectroscopy. The spectra in the vibrational mid-infrared region (1800-1550 cm-1) of hydrated and partially dehydrated reaction centers were investigated from 50 ps to 4 ns after photoinitiation of the electron transfer. Features in the infrared difference spectra were identified with both protein and redox cofactor vibrational modes and correlated with electron transfer events whose kinetics were measured in the infrared and visible regions. The observed protein response is confined to a few amide I transitions (1644 cm-1, 1661 cm-1, 1665 cm-1) and carboxylic residues (1727 cm-1). About 85% of the observed signal corresponded to alterations in the cofactor-associated ester and keto carbonyls. The amide I and carboxylic transitions appeared prior to 50 ps, suggesting that the primary electron transfer event is coupled with a specific piece of the protein backbone and to glutamic or aspartic residues nearby the special pair. Infrared absorption changes accompanying bacteriochlorophyll-dimer cation formation dominated the signal at all times investigated. Infrared spectral changes observed in hydrated and partially dehydrated reaction centers were distinctly different; a band at 1665 cm-1 with a spectral width of 6 cm-1 in the hydrated protein, corresponding to a protein amide I bleach, was not present in the dehydrated film. These differences are discussed in terms of the markedly different electron transfer kinetics observed in the presence of water.

Picosecond dynamics of bacteriorhodopsin, probed by time-resolved infrared spectroscopy

The photoinduced reaction cycle of bacteriorhodopsin (BR) has been studied by means of a recently developed picosecond infrared spectroscopic method at ambient temperature. BR - K difference spectra between 1560 and 1700 cm-1 have been recorded at delay times from 100 ps to 14 ns. The spectrum remains unchanged during this period. The negative difference OD band at 1660 cm-1 indicates the peptide backbone responds within 50 ps. A survey in the region of carboxylic side chain absorption around 1740 cm-1 reveals that perturbations of those groups, present in low-temperature FTIR spectra, are not observable within 10 ns, suggesting a slow conformational change.

[The significance of antibodies to Pasteurella haemolytica A1 in the colostrum of cows and blood serum of calves]

Antibodies to P. haemolytica were detected in colostral sera of cows and blood sera of calves by means of indirect haemagglutination (IHA) and ELISA. The ELISA titres of the colostral sera of the dams and of the blood sera of the calves showed a significantly positive correlation. There is a positive correlation between the titres of the two serological methods. The results of the challenge infection with P. haemolytica A 1 do not show a correlation between the titres and the severity of the disease. Heifer calves, however, developed more severe pneumonias than calves from older cows.

High-repetition-rate infrared-pump, infrared-probe spectrometer

A method for generating two independently tunable 25-ps infrared pulses at 500 Hz was demonstrated. The apparatus is based on two dye lasers, a regenerative amplifier, and two lithium iodate optical-parametric amplifiers. Using the pump-probe technique, we measured the lifetime of the excited vibrational-state absorption of tungsten hexacarbonyl in solution.

Ultrafast infrared spectroscopy of bacteriorhodopsin

Picosecond infrared spectroscopy is developed and used for the first time to study the dynamics of photoexcited bacteriorhodopsin (BR). Both spectral and time-resolved data are obtained. The results open an entirely new approach to investigations of the BR photocycle. The infrared difference spectrum (K minus BR570) recorded at ambient temperature between 1,560 and 1,700 cm-1 is not identical with the spectrum reported for a frozen sample. Three bands of the K state at 1,622, 1,610, and 1,580 cm-1 and the bleaching at 1,637 cm-1 (C = NH stretch) are seen. These new spectral lines appear in less than 10 ps.

Strategies of disattention and auditory hallucinations in schizophrenics

Disattentional strategies used by schizophrenics to attenuate auditory stimulation from the environment were proposed as extraordinary conditions of attention which facilitate the misperception of lexical thought as a voice and create an auditory hallucination. Two strategies were studied. The switching strategy involved concentration upon an external visual display to prevent a clearly audible list of words from registering. The holding strategy required mentally repeating a word in the list so as to ignore the words that followed. Process (N = 32) and reactive (N = 32) schizophrenics, 46 of whom had a history of auditory hallucinations, served as subjects. Effectiveness of the two disattentional strategies was tested by subsequent inability of the schizophrenic to recognize words from the taped list. Process schizophrenics with auditory hallucinations were able to use switching effectively but not holding. In contrast, reactive schizophrenics suffering auditory hallucinations successfully used holding but not switching. Both effects were confirmed relative to hallucinating controls given standard memory instructions. Strategy effects were not apparent in nonhallucinating schizophrenics. These results suggest that different disattentional strategies may have been practiced by hallucinating schizophrenics in keeping with their premorbid status and style of attention deployment. A proposal functionally relating disattention to the genesis of auditory hallucinations was suggested.