Light-dependent delay in the falling phase of the retinal rod photoresponse.

Using suction electrodes, photocurrent responses to 100-ms saturating flashes were recorded from isolated retinal rods of the larval-stage tiger salamander (Ambystoma tigrinum). The delay period (Tc) that preceded recovery of the dark current by a criterion amount (3 pA) was analyzed in relation to the flash intensity (If), and to the corresponding fractional bleach (R*0/Rtot) of the visual pigment; R*0/Rtot was compared with R*s/Rtot, the fractional bleach at which the peak level of activated transducin approaches saturation. Over an approximately 8 ln unit range of I(f) that included the predicted value of R*s/Rtot, Tc increased linearly with ln I(f). Within the linear range, the slope of the function yielded an apparent exponential time constant (tau c) of 1.7 +/- 0.2 s (mean +/- S.D.). Background light reduced the value of Tc measured at a given flash intensity but preserved a range over which Tc increased linearly with ln I(f); the linear-range slope was similar to that measured in the absence of background light. The intensity dependence of Tc resembles that of a delay (Td) seen in light-scattering experiments on bovine retinas, which describes the period of essentially complete activation of transducin following a bright flash; the slope of the function relating Td and ln flash intensity is thought to reflect the lifetime of photoactivated visual pigment (R*) (Pepperberg et al., 1988; Kahlert et al., 1990). The present data suggest that the electrophysiological delay has a similar basis in the deactivation kinetics of R*, and that tau c represents TR*, the lifetime of R* in the phototransduction process. The results furthermore suggest a preservation of the "dark-adapted" value of TR* within the investigated range of background intensity.     

Do arachnoid cysts grow?

Summary The volumes of intracranial arachnoit cysts were measured in 136 CT scans of 86 patients. Absolute and relative cyst size was calculated. Left hemisphere and middle cranial fossa location prevailed. A slight negative correlation of relative cyst size with age (r=–0.21, NS) disappeared when analysis was restricted to the adult age group (20 years). After the sample was divided into two groups according to relative cyst size (cysts less than mean volume vs cysts greater than mean volume), small AC showed no correlation with age, while large AC correlated positively with age (r=0.79,P<0.05). A subgroup of large AC appears to expand with time, while the majority of small AC remain unchanged.     

Possibilities of application of the fixateur externe at the femur - indications, results (author's transl)

Besides the methods of screwing of plates and medullary nailing, the fixateur externe (F.E.) is another method which can be considered for treating bone fractures at the femur, F.E. being an exceptional indication. In fresh fractures of the femur, open fractures of the second and third grade as well as debris and multiple-plane fractures are typical indications for F.E. Over and above, F.E. is almost always indicated as an emergency measure in case of initial inoperability (polytrauma, shock, loss of blood, craniocerebral trauma) or continuing general inoperability. F.E. has been found useful to an even greater extent especially in old fractures, refractures, pseudarthroses and infected pseudarthroses. Combined treatment of the infected pseudarthroses with F.E. and Septopal balls has proved particularly effective. The special advantages of F.E. application at the femur are blood-saving surgery requiring relatively little time and technical equipment, avoidance of surgically conditioned infection risk in the fractured region, avoidance of additional denudation of free fracture fragments, long-term applicability, good external stabilization with selective possibility between compression, distraction and neutral positioning of the fractured area, postoperative treatment without dressing, and free access to the fractured area without interfering with the F.E.; furthermore, exchangeability of the F.E., possibility of correcting the position and axis without surgical intervention, non-fixation of the adjacent joints and maintenance of physiotherapeutic treatment possibilities. F.E. is "panacea" and should not be applied without exact knowledge of the static and mechanical and biomechanical conditions and effects. Before resorting to F.E. this must be carefully weighed against the use of internal osteosynthesis methods. It is not a rival method to plate screwing and medullary nailing but rather an auxiliary system whenever these methods are inapplicable or would entail disadvantages.     

Particle release in extracorporeal low-density lipoprotein lowering therapies

Release of microparticles into the blood during extracorporeal circulation must be kept low because of possibly serious acute and chronic adverse effects. Concentration and size distribution of microparticles were measured during simulated treatments (n = 7) on original equipment for 2 standard low-density lipoprotein (LDL) elimination procedures (DALI 750, Fresenius AG, St. Wendel, Germany and Liposorber, Kaneka Corporation, Osaka, Japan) and compared to hemofiltration solutions. For both systems as well as in hemofiltration solutions, the mean particle concentrations in 500 ml portions gathered from the efferent blood line stayed below 10% of pharmacopoeia standards for infusion solutions (United States Pharmacopoeia, European Pharmacopoeia) in all measured size classes. Although particle concentrations were comparable in all systems, the mean total number of particles > or =2 microm released per session was lowest in the DALI (167,000) compared to the Liposorber (465,000) and hemofiltration solutions (2,240,000). This was mainly due to different total processed blood volumes necessary to achieve the required LDL reduction.     

Diagnostic imaging in femur head necrosis

Diagnosis of avascular necrosis (AVN) of the hip has been improved by the technical progress of imaging modalities during the last decade. For a long period, only plain radiographs had been available. Scintigraphy and computed tomography contributed to differential diagnosis and early detection of bone necrosis. In the meantime, MR imaging has gained special value in the evaluation of AVN. It is now the method of choice for early detection as well as for assessment in later stage disorders. Using the ARCO system, all imaging modalities and their diagnostic viability are described. Findings regarding the different stages of AVN are correlated to tissue-specific changes.