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

This paper presents a combined spectroscopic and theoretical analysis of a trinuclear [Pd3{Si(mt(Me))3}2] complex (mt(Me) = methimazole) which has been demonstrated to be a potential catalyst for coupling reactions. It is a highly symmetric model system (D3 in the electronic ground state) for the investigation of electronic states and the structure of polynuclear transition metal complexes. Different time-resolved IR spectroscopic methods covering the femtosecond up to the microsecond range as well as density functional computations are performed to unravel the structure and character of this complex in the electronically excited state. These are the first time-resolved IR studies on a trinuclear Pd complex. Based on the interplay between the computational results and those from the IR studies a (3)A state is identified as the lowest lying triplet state which has C2 symmetry.

In-depth exploration of the photophysics of a trinuclear palladium complex.

A detailed theoretical and spectroscopic study on the electronically excited states of a trinuclear palladium complex is presented both in the gas phase and solution. The application of DFT and TDDFT methods as well as a variety of spectroscopic methods to the chosen complex [Pd3{Si(mt(Me))3}2] (1, mt(Me) = methimazole) leads to the first detailed analysis of the photophysics of a symmetric trinuclear complex. In combination with the calculations, energies, structures and lifetimes of the excited electronic states (with an (3)A1 state as the lowest one) are characterized by applying the resonant-2-photon-ionization method in a molecular beam experiment as well as luminescence, time-correlated single photon counting and excited state femtosecond absorption spectroscopy in solution. These investigations are of fundamental interest to analyze photophysical properties of metal containing complexes on a molecular level.

Point-defect interactions in electron-irradiated titanomagnetites--as analysed by magnetic after-effect spectroscopy on annealing within 80 K < Ta < 1200 K.

During high-temperature growing of titanomagnetite single crystals (Fe(2.8-Δ)Ti(0.2)O(4), Δ < 0.005) in oxygen enriched atmospheres, specific Ti(4+)- and vacancy-based defect configurations are induced, giving rise to magnetic after-effect (MAE) spectra with peaks near 450, 200 and 65 K. The atomistic mechanisms of these relaxations are checked by exposing the crystals to low-temperature (80 K) electron (e(-)) irradiation and subsequent analysis of the interactions between radiation-induced and lattice-inherent defects on annealing over the range 80 K ≤ T(a) < or equal 1200 K. Within this interval, three characteristic temperature ranges are distinguished: (a) 80 K < T(a) < 500 K, revealing vigorous interactions between radiation-induced and inherent defect configurations, thus demonstrating their common point-defect nature; (b) 500 K < T(a) < 900 K wherein the MAE spectra re-assume, qualitatively, their initial structure with, however, mutually modified amplitude ratios; (c) 900 K < T(a) < 1200 K, being characterized by the complete annihilation of all MAEs but, interestingly, also the thermally induced re-appearance of vacancies and related defect configurations. The recovery kinetics of all prominent processes are numerically analysed and discussed with respect to their underlying atomistic mechanisms.

[Fast and efficient healing of scleroderma-associated acral ulcers with sildenafil]. / Rasche Abheilung von akralen Ulzera bei systemischer Sklerodermie unter Sildenafil.

Acral ulcers in patients with progressive systemic sclerosis (PSS) are often recalcitrant to therapy. Sildenafil, an inhibitor of phosphodiesterase-5, dilates small arteries by increasing endothelial cGMP. Oral administration of sildenafil to a 35-year-old white male patient suffering from incapacitating PSS with severe pulmonary arterial hypertension and acral ulcers induced a clinically significant reduction in dyspnea and increase in walking distance within one week as well as complete and long-lasting healing of all ulcers within five weeks. This case demonstrates the efficacy of sildenafil in the treatment of scleroderma-associated refractory acral ulcers.

Microstructural insight into pedestrian pelvic fracture as assessed by high-resolution computed tomography.

Pelvic and femoral neck bone surface strains were recorded in five full-body human cadaver vehicle-pedestrian impacts. Impacts were performed at 40 km/h using automotive front ends constructed to represent those used in previously reported finite element simulations. While experimental kinematics and bone strains closely matched model predictions, observed pelvic fractures did not consistently agree with the model, and could not be solely explained by vehicle geometry. In an attempt to reconcile injury outcome with factors apart from vehicle design, a proxy measure of subject skeletal health was assessed by high-resolution quantitative computed tomography (HRqCT) of the femoral neck. The incidence of hip/pelvis fracture was found to be consistent with low volumetric bone mineral density and low trabecular bone density. This finding lends quantitative support to the notion that healthy trabecular architecture is crucial in withstanding non-physiological impact loads. Furthermore, it is recommended that injury criteria used to assess vehicle safety with regard to pedestrians consider the increased susceptibility of elderly victims to pelvic fracture.

Pressure aberrations inside the spinal canal during rear-end impact.

Minor soft tissue injuries of the cervical spine increasingly pose problems in public health. Such injuries are conveyed particularly often in rear-end automobile collisions at low impact speeds and it has been established that they may be associated with long-term impairment. As a possible cause for this type of injury it has been hypothesized that pressure pulses induced in cervical fluid compartments during the impact could damage the membrane of spinal nerve cells. To date, animal as well as cadaver experiments performed support this hypothesis. A theoretical analysis has been undertaken in order to investigate the pressure and flow pulse emerging in a cervical fluid compartment under conditions representing rear-end impacts with a Dv of 15 km/h. Using the finite element (FE) method, a three-dimensional model of the cervical spine was developed. The model consists of eight vertebrae (C1-T1), the intervertebral discs, the intervertebral joints, all the major ligaments, most of the neck muscles and the head. Additionally, a typical venous blood vessel was included. To determine the pressure behaviour inside the blood vessel, fluid-structure interaction was taken into account. For the time interval including the development of the S-shape, the pressure pulses were calculated and found to be in qualitative agreement with the reported measurements. The shear stresses acting on the vessel wall can be determined from the associated flow pulses. An extrapolation of the results into the interstitial space where nerve cells are located at this stage does not allow assessment of whether a damage threshold may be reached.

Whiplash injury: cases with a long period of sick leave need biomechanical assessment.

A total of 668 cases of cervical spine disorders (CSD) sustained in automotive collisions were analysed. All cases had a minimum sick leave duration of 4 weeks. To evaluate these cases a scheme was developed that takes into account technical, medical, and biomechanical aspects. For each case, the delta-v value of the underlying collision was estimated, the medical files were analysed, and a QTF (Québec Task Force) grade was assigned. In addition, the medical history of the patient was reviewed. It was found that the QTF grade for patients with pre-existing damage of the neck or pre-existing signs differed significantly from those patients without such a history. The overall assessment, which stated the extent to which the symptoms claimed could be explained by the impact, was also found to be significantly influenced by a history of neck injury. The results of the study showed that in about 50% of the cases where the technical analysis alone would not suggest that the symptoms shown could be explained by the impact, those symptoms could be explained when patient history and the collision circumstances were taken into consideration. It also found that medical evaluation based on a QTF grade alone cannot assess the explicability of claimed CSD without taking into account the collision circumstances. Therefore, the assessment of critical individual relevant biomechanical factors is necessary.

Biomechanical assessment of soft tissue neck injuries in cases with long sick leave times.

A database was established by collecting 919 cases of claimed cervical spine disorders (CSDs) sustained in automotive accidents. All cases had a sick leave time of more than 4 weeks. Data was obtained from a major Swiss accident insurer. An assessment scheme was developed that took into account technical, medical, and biomechanical aspects. All cases were evaluated according to this scheme. The overall biomechanical assessment, that stated the extent to which the symptoms claimed could be explained by the impact, was found to be significantly influenced by the patient's history of CSD in terms of preexisting damage or preexisting symptoms. In 52% of the assessed cases, the CSD claimed could be explained with a combination of neck loading and also by considering the patient's medical history. Performing a solely technical analysis of the collision circumstances or a purely medical evaluation based on a Quebec Task Force (QTF) grade alone are insufficient to assess the accident-related explicability of claimed CSD. Biomechanically relevant individual factors have to be considered.

Probing functional perfection in substructures of ribonuclease T1: double combinatorial random mutagenesis involving Asn43, Asn44, and Glu46 in the guanine binding loop.

Combinatorial random mutageneses involving either Asn43 with Asn44 (set 1) or Glu46 with an adjacent insertion (set 2) were undertaken to explore the functional perfection of the guanine recognition loop of ribonuclease T(1) (RNase T(1)). Four hundred unique recombinants were screened in each set for their ability to enhance enzyme catalysis of RNA cleavage. After a thorough selection procedure, only six variants were found that were either as active or more active than wild type which included substitutions of Asn43 by Gly, His, Leu, or Thr, an unplanned Tyr45Ser substitution and Glu46Pro with an adjacent Glu47 insertion. Asn43His-RNase T(1) has the same loop sequence as that for RNases Pb(1) and Fl(2). None of the most active mutants were single substitutions at Asn44 or double substitutions at Asn43 and Asn44. A total of 13 variants were purified, and these were subjected to kinetic analysis using RNA, GpC, and ApC as substrates. Modestly enhanced activities with GpC and RNA involved both k(cat) and K(M) effects. Mutants having low activity with GpC had proportionately even lower relative activity with RNA. Asn43Gly-RNase T(1) and all five of the purified mutants in set 2 exhibited similar values of k(cat)/K(M) for ApC which were the highest observed and about 10-fold that for wild type. The specificity ratio [(k(cat)/K(M))(GpC)/(k(cat)/K(M))(ApC)] varied over 30 000-fold including a 10-fold increase [Asn43His variant; mainly due to a low (k(cat)/K(M))(ApC)] and a 3000-fold decrease (Glu46Ser/(insert)Gly47 variant; mainly due to a low (k(cat)/K(M))(GpC)) as compared with wild type. It is interesting that k(cat) (GpC) for the Tyr45Ser variant was almost 4-fold greater than for wild type and that Pro46/(insert)Glu47 RNase T(1) is 70-fold more active than the permuted variant (insert)Pro47-RNase T(1) which has a conserved Glu46. In any event, the observation that only 6 out of 800 variants surveyed had wild-type activity supports the view that functional perfection of the guanine recognition loop of RNase T(1) has been achieved.

Biomechanical assessment of soft tissue cervical spine disorders and expert opinion in low speed collisions.

The multidisciplinary research of injury mechanisms and injury prevention requires the assessment of the technical and biomechanical circumstances of a collision; moreover, the causality assessment in the individual cases is facilitated by taking these aspects into account. In fact, only specially trained engineers and biomechanical experts are in a position to evaluate these relevant basic facts. In many crucial court cases, important technical factors such as collision angle, structural stiffness, extent of intrusion and the vehicle's velocity change are often ignored. The purely medical causality assessment is often based only on a coincidence of time of the 'accident' and the onset of the disorders. Unfortunately, statements about the 'accident speed' or the nebulous 'accident energy' are often made by clinicians with neither a proper collision documentation nor the necessary biomechanical and technical background. In order to overcome shortcomings of injury causality assessment as well as the terminology associated with soft tissue cervical spine injuries, a subdivision of the term 'accident severity' into four classes is proposed. Consequently, an 'accident severity assessment' can only be performed by a collaboration of four corresponding classes of experts, i.e. the engineer (dynamic loading of the vehicle), the biomechanical expert (biomechanical loading of the occupant), the physician (clinically diagnosable injuries), and eventually the psychiatrist (subjective sequelae individually experienced by the victim).

A Review of the Magnetic Relaxation and Its Application to the Study of Atomic Defects in α-Iron and Its Diluted Alloys.

This review presents a comprehensive survey on intensive studies performed during the last decades on point defect reactions on α-iron (α-Fe) and its diluted alloys. Our intention is to give an actual account of the knowledge accumulated on this subject, as it has been obtained predominantly by means of the magnetic after-effect (MAE) spectroscopy. After a concise introduction into the theoretical and experimental fundamentals of this technique, the main concern is focused on the presentation and detailed discussion of the MAE spectra arising - after low-temperature electron (e-)- or neutron(n)-irradiation and subsequent annealing - in: (i) high-purity α-Fe and α-Fe doped with (ii) substitutional solutes (like Ni, V, Al, Cu, Ti, Be, Si, Mn, …) or (iii) interstitial solutes (like O, H, C, N). During the course of systematic annealing treatments, these respective spectra undergo dramatic variations at specific temperatures thereby revealing in great detail the underlying intrinsic reactions of the radiation-induced defects, i.e., reorientation, migration, clustering, dissolution and finally annihilation. In alloyed Fe systems the corresponding reaction sequences are even multiplied due to additional interactions between defects and solute atoms. Most valuable information concerning formation-, dissociation- and binding enthalpies of small, mixed clusters (of the type C i V k , N i V k ; i, k ≥ 1) has been obtained in high-purity α-Fe base material which, after charging with C or N, had been e--irradiated. Concerning the basic recovery mechanisms in α-Fe, two complementary results are obtained from the analysis of the various systems: (i) in high-purity and substitutionally alloyed α-Fe the recovery in Stage-III (200 K) is governed by a three-dimensionally migrating (H M I = 0.56 eV) stable interstitial (dumb-bell); (ii) following the formation and dissociation kinetics of small clusters (C1V k , N1V k ) in interstitially alloyed α-Fe the migration enthalpy of the monovacancy must hold the following relation H M N (0.76 eV) < H M C (0.84 eV) < H M V1. These results are in clear agreement with the so-called two-interstitial model (2IM) in α-Fe - a conclusion being further substantiated by a systematic comparison with the results obtained from nonrelaxational techniques, like i.e. positron annihilation (PA), which by their authors are preferentially interpreted in terms of the one-interstitial model (1IM).

Three-dimensional structure of ribonuclease T1 complexed with an isosteric phosphonate substrate analogue of GpU: alternate substrate binding modes and catalysis.

The X-ray crystal structure of a complex between ribonuclease T1 and guanylyl(3'-6')-6'-deoxyhomouridine (GpcU) has been determined at 2. 0 A resolution. This ligand is an isosteric analogue of the minimal RNA substrate, guanylyl(3'-5')uridine (GpU), where a methylene is substituted for the uridine 5'-oxygen atom. Two protein molecules are part of the asymmetric unit and both have a GpcU bound at the active site in the same manner. The protein-protein interface reveals an extended aromatic stack involving both guanines and three enzyme phenolic groups. A third GpcU has its guanine moiety stacked on His92 at the active site on enzyme molecule A and interacts with GpcU on molecule B in a neighboring unit via hydrogen bonding between uridine ribose 2'- and 3'-OH groups. None of the uridine moieties of the three GpcU molecules in the asymmetric unit interacts directly with the protein. GpcU-active-site interactions involve extensive hydrogen bonding of the guanine moiety at the primary recognition site and of the guanosine 2'-hydroxyl group with His40 and Glu58. On the other hand, the phosphonate group is weakly bound only by a single hydrogen bond with Tyr38, unlike ligand phosphate groups of other substrate analogues and 3'-GMP, which hydrogen-bonded with three additional active-site residues. Hydrogen bonding of the guanylyl 2'-OH group and the phosphonate moiety is essentially the same as that recently observed for a novel structure of a RNase T1-3'-GMP complex obtained immediately after in situ hydrolysis of exo-(Sp)-guanosine 2',3'-cyclophosphorothioate [Zegers et al. (1998) Nature Struct. Biol. 5, 280-283]. It is likely that GpcU at the active site represents a nonproductive binding mode for GpU [Steyaert, J., and Engleborghs (1995) Eur. J. Biochem. 233, 140-144]. The results suggest that the active site of ribonuclease T1 is adapted for optimal tight binding of both the guanylyl 2'-OH and phosphate groups (of GpU) only in the transition state for catalytic transesterification, which is stabilized by adjacent binding of the leaving nucleoside (U) group.

Upstream subsite interactions for oligonucleotide binding with ribonuclease T1.

Ribonuclease T1 (RNase T1) specifically cleaves RNA at guanylyl residues. Previous studies revealed the presence of an enzyme-subsite interaction for adenosine residues of ApGpC and ApGpU substrates (Osterman and Walz (1979) Biochemistry 10, 1984-1988). The binding of ApG and 2'-deoxyadenylyl-(3',5')-guanosine (dApG) with RNase T1 was studied in the pH range 5-9 using ultraviolet difference spectroscopy. The association constants for these dinucleoside monophosphates showed the same pH dependence both of which differed at low pH values with that for the methyl phosphoester of 5'-GMP (MepG). This difference suggested that binding of the adenosine group is strongly dependent on the deprotonation of an enzyme/ligand group with a pKa value of < or = 4.8. delta G zero for ApG binding minus that for MepG at pH > 6 yielded a delta delta G of -1.17 +/- 0.10 kcal/mol which is a measure of the contribution of the adenosine moiety to binding. ApG bound more tightly than dApG with a mean delta delta G value of -0.73 +/- 0.10 kcal/mol which demonstrated the involvement of the adenosine 2'-OH group in binding. These and other comparisons indicated that delta delta G for maximal binding the adenine base per se was -0.44 kcal/mol. delta delta G for binding pdApdG minus that for dApdG (-0.94 kcal/mol) suggested an enzyme subsite for the phosphomonoester group of former ligand.

Adult-male-specific S-warfarin (11S-OH) and progesterone (20 beta-OH) keto-reductases in rat hepatic microsomes are not identical.

Adult-male-specific reductase activities in rat hepatic microsomes use NADPH to reduce S-warfarin and progesterone to their 11S-OH and 20 beta-OH products, respectively (Apanovitch et al. (1992) Biochem. Biophys. Res. Commun. 184, 338-346). When microsomes were treated with increasing concentrations of detergent, S-warfarin (11S-OH) reductase (SW(11S)R) activity was subject to monophasic activation by Triton X-100, monophasic inhibition by sodium cholate, and, activation followed by inhibition with either CHAPS or dodecyl-beta-D-maltoside. A non-dialyzable, heat-sensitive factor in rat and rabbit sera activates microsomal SW(11S)R activity six- to eight-fold. Similar detergent inhibitions but no detergent or serum activations were observed for progesterone (20 beta-OH) reductase (P(20 beta)R) activity. A significant amount of SW(11S)R activity was lost during purification regardless of whether the detergent used for solubilization was activating or inhibiting. Octyl-Sepharose, hydroxyapatite, DEAE-cellulose and carboxymethyl matrices were used to partially purify SW(11S)R. P(20 beta)R activity co-purified with SW(11S)R and the most purified fraction contained two major and several minor polypeptides. Partially purified SW(11S)R is activated by detergents, serum, and salt. These and previous results indicate that SW(11S)R and P(20 beta)R are not identical even though they are both adult male-specific, integral membrane proteins apparently having their active sites exposed on the cytoplasmic surface of the endoplasmic reticulum.

In vitro hydrolysis of gliadin and casein peptides: secondary defect in coeliac disease shown by organ culture.

BACKGROUND: Small-intestinal organ culture was used as an in vitro model of coeliac disease, studying biopsy specimens from patients with coeliac disease, cow's milk allergy, and controls. METHODS: Organ culture incubations were done using the pure gliadin peptide B3144 (amino acid sequences 3-56 of alpha-type gliadins) and a control peptide from casein (amino acid sequences 152-193 of alpha s1-casein). The importance of using negative controls was stressed by non-specific tissue damage. By reversed-phase high-performance liquid chromatography of organ culture supernatants, 27 specimens were further investigated. RESULTS: There was good retrieval of peptide calibration peaks after culture. Qualitative and quantitative evaluation of chromatography runs showed degradation of at least 29% of B3144 and 37% of Cas-P. Normal mucosa (controls and coeliac patients on a gluten-free diet) was able to hydrolyse peptide fractions completely, whereas incubation with damaged mucosa (coeliac disease, cow's milk allergy) left initial peptides. CONCLUSION: It is concluded, using a pure single gliadin peptide, that deficient peptide hydrolysis in coeliac disease was a secondary event.

[Severe perforating eye injury caused by an air bag in a traffic skid accident]. / Schwere perforierende Augenverletzung durch Airbag bei Schleuderunfall.

BACKGROUND: After a penetrating injury of the eye following a car accident the driver demanded accurate investigations by the Institute for Legal Medicine of Zurich concerning the security of the equipment, especially the airbag. This led to an astonishing explication of the mechanism of the injury, not without consequences for safety measures for drivers and front seat passengers in air bag equipped cars. CASE REPORT: Due to a relatively harmless accident, the driver suffered from a severe penetrating injury of the right eye after the airbag deployed. The front seat passenger, having the seat belts fastened, was not injured. The accident was investigated by the Institute of Legal Medicine of Zurich. RESULTS: The analysis of the accident showed that the airbag had deployed properly. The cover of the airbag showed no defects of substance. With the precise examination of the interior of the car a broken tobacco pipe came to light. CONCLUSIONS: In this case not the airbag itself but a tobacco pipe held in the hand by the driver during the airbag ignition caused a severe injury of the eye. This case report illustrates the hazard of having any rigid object between the occupant and the deploying air bag. In conclusion, the drivers and front seat passengers of an airbag equipped car can only profit from the considerable security gain, if they know about these risks and adapt their behaviours to the new surroundings, but also the car manufactures have to instruct the customers properly.

Compatibility considerations for low-mass rigid-belt vehicles.

A number of staged impacts performed by our group with the aid of a test device representing a low-mass vehicle (LMV) indicates that a rigid-belt body (RBB) is a valid means for providing adequate occupant safety also for LMVs in the strict sense (curb mass less than 600 kg). The RBB concept raises the problem of compatibility, however. Ideally, the deformability of car front structures should increase with increasing vehicle weight in order to ascertain compatibility. Published data on frontal deformation characteristics substantiate in contrast that conventional cars today exhibit an opposite behaviour. To evaluate the compatibility properties of ultrastiff LMVs, two crash experiments were performed along with a theoretical model analysis. An LMV with a mass of 680 kg (including batteries, 50% mass of two dummies, instrumentation) designed according to the RBB concept and a conventional care of 1320 kg--(equivalent loading conditions as LMV)--were crashed at 56 km/h in a frontal direction against a deformable barrier (FMVSS 214). Furthermore, a mathematical model was based on estimated deformation characteristics of conventional vehicles to predict intrusion distances into the FMVSS barrier in hypothetical frontal crashes with 56 km/h. The results indicate that due to its low mass an LMV does not represent an excessive compatibility problem for other car occupants in spite of the stiff RBB characteristics.

Airbag deployment and eye perforation by a tobacco pipe.

Airbags have been shown to reduce injuries and save the lives of car occupants in a crash. Like any protection system, airbags potentially introduce some new risks if no appropriate countermeasures are taken. A case of a relatively moderate frontal impact is described where the driver of an airbag-equipped car suffered a severe penetrating eye injury after the airbag deployed. Since the airbag fabric itself was excluded as an injury-producing structure, other objects such as eyeglasses, a wrist-watch, a bracelet, and a large finger ring had to be assessed. The investigation of the car interior as well as the morphologic details of the injuries to the eye and the face revealed that the most likely candidate for the injury was a tobacco pipe, which was probably being held in one hand and was broken apart by the deploying airbag and projected into the face of the driver. This case illustrates the hazard of having any rigid object between the occupant and the deploying airbag. The desirability of warning car occupants of the potential hazards which can result from today's protection systems is also discussed.

[Biomechanical aspects of injuries of the cervical vertebrae]. / Biomechanische Aspekte der HWS-Verletzungen.

A biomechanical expert opinion on the injury mechanism is necessary only in a few cases. However, the judgement of these cases is extremely compromised if the mechanics of injury are described incorrectly in the clinical report. Since the mechanism of neck injuries is very complex, the physician without biomechanical training should concentrate on the familiar clinical findings; The relevant mechanisms of indirect neck trauma are (a) a non-head-contact mechanism (hyperflexion or hyperextension, hypertranslation, acceleration) and (b) head contact leading to compression, hyperflexion, hyperextension and/or hypertranslation. A non-head-contact mechanism occurs, for example, in the case of rear end impact without head restraint (hyperextension) or a frontal collision involving a belted occupant (hyperflexion), without head impact. The term "whiplash" is misleading and incorrect: It presumes a virtually non-existent two-phase movement back and forth (or vice versa), and it confuses the physical criterion mechanism and the anatomical or morphological criterion injury, e.g. distortion, sprain etc. A head-contact mechanism involves momentum exerted from the head on the neck. Again, the anatomical and morphological terms are the same, but the mechanism is different. With a contact mechanism and a non-contact mechanism, not only a hyperflexion or a hyperextension can occur; in the first phase of the impact, a shearing force between the upper vertebral bodies (C0-C2) may load the intervertebral structures by hypertranslation.

Genetic and developmental diversity of hepatic cytochromes P450. Warfarin and progesterone metabolism by hepatic microsomes from four inbred strains of rat.

Hepatic microsomes from immature and sexually mature male and female ACI/SEGHsd, F344/NHsd, SHR/NHsd, and WKY/NCrl inbred rats were used to study cytochrome P450 (P450)-catalyzed oxidations of progesterone and both enantiomers of warfarin. Strains were selected on the basis of their different, homozygous allelic compositions for CYP2C11 and CYP2C13 (Rampersaud and Walz, 1992), but no correlations with the microsomal activities were observed. However, correlations were made regarding catalytic activities and the developmental control of CYP2A1 and CYP2C11 levels in microsomes. Other correlations were found for reactions of both warfarin enantiomers at the same atom or for a given enantiomer at different positions, and these appear to involve several P450 isozymes. Strain-dependent activity differences mainly involved the SHR/NHsd and WKY/NCrl strains. WKY/NCrl rats were the most unique strain, having low levels of CYP2C11 in adult males compared with the other inbreds but relatively high S-warfarin 4'- and 6-hydroxylase activities in immature animals of both sexes and adult females. These results suggest that the regulation and/or allozymic composition of hepatic P450s are different for WKY/NCrl rats, which makes them a poor choice as "normotensive controls" in comparison with hypertensive SHR rats.