Medizin - Open Access LMU - Teil 07/22 Archiv

The nuclear cyt-2-1 mutant of Neurospora crassa is characterized by a gross deficiency of cytochrome c (Bertrand, H., and Collins, R. A. (1978) Mol. Gen. Genet. 166, 1-13). The mutant produces mRNA that can be translated into apocytochrome c in vitro. Apocytochrome c is also synthesized in vivo in cyt-2-1, but it is rapidly degraded and thus does not accumulate in the cytosol. Mitochondria from wild-type cells bind apocytochrome c made in vitro from either wild-type or cyt-2-1 mRNA and convert it to holocytochrome c. This conversion depends on the addition of heme by cytochrome c heme lyase and is coupled to translocation of cytochrome c into the intermembrane space. Mitochondria from the cyt-2-1 strain are deficient in the ability to bind apocytochrome c. They are also completely devoid of cytochrome c heme lyase activity. These defects explain the inability of the cyt-2-1 mutant to convert apocytochrome c to the holo form and to import it into mitochondria.

One hundred twenty-six bilateral selective arteriographic examinations of the iliopudendal vascular tree were performed after comprehensive multidisciplinary evaluation in patients with chronic erectile dysfunction. Best imaging results were obtained by performing the arteriography under epidural anesthesia after intracavernous injection of a vasoactive drug combination. The arteriography is mandatory prior to revascularization procedures. It is further indicated in primary erectile dysfunction and posttraumatic erectile failure. The importance of cavernosography and selective arteriography in primary erectile dysfunction is stressed. Increasing knowledge about the influence of vasoactive drugs on penile hemodynamics has led to its application in diagnosis and therapy of erectile dysfunction. Pharmacocovernosography, Doppler-ultrasound of penile arteries after intracavernous injection of a vasoactive drug combination, and pharmacoarteriography are refined techniques to prove a vascular etiology of erectile dysfunction. The results of the morphologic studies of the vascular system are correlated with functional testing of erectile capacity by intracavernous application of a papaverinephentolamine drug combination.

In 63% of 265 patients with erectile dysfunction a relevant arterial inflow disturbance was found by Doppler ultrasound examination. Correlation between Doppler and arteriography in 58 patients showed an accuracy of 95% in detecting penile arteries and an accuracy of 91% in discovering a pathological arterial pattern (arterial anomaly or arteriosclerotic obstruction). In 15 patients the arterial inflow was measured additionally by Doppler ultrasound technique after intracavernosal injection of vasoactive drugs (IIVD) (7.5 mg papaverine and 0.25 mg phentolamine). This technique proved to be more reliable than in the flaccid state and markedly facilitated localization and assessment of pathological changes of the cavernosal arteries.

Transport of nuclear-encoded precursor proteins into mitochondria includes proteolytic cleavage of aminoterminal targeting sequences in the mitochondrial matrix. We have isolated the processing activity from Neurospora crassa. The final preparation (enriched ca. 10,000-fold over cell extracts) consists of two proteins, the matrix processing peptidase (MPP, 57 kd) and a processing enhancing protein (PEP, 52 kd). The two components were isolated as monomers. PEP is about 15-fold more abundant in mitochondria than MPP. It is partly associated with the inner membrane, while MPP is soluble in the matrix. MPP alone has a low processing activity whereas PEP alone has no apparent activity. Upon recombining both, full processing activity is restored. Our data indicate that MPP contains the catalytic site and that PEP has an enhancing function. The mitochondrial processing enzyme appears to represent a new type of “signal peptidase,” different from the bacterial leader peptidase and the signal peptidase of the endoplasmic reticulum.

Of over 300 patients with erectile dysfunction, 186 were selected for intracavernosal autoinjection therapy with a standardized papaverine-phentolamine mixture. A total of 156 patients performed 4,813 protocol autoinjections with a minimum of 10 and a maximum of 230 per patient. The dose that induced a full erection at the hospital could be reduced under home conditions by a mean of 35 per cent. Systemic side effects were not observed. The most inconvenient local side effects were prolonged erections in 24 patients in diagnostic use and in 3 patients in therapeutic use. These were treated easily without further consequences.

A total of 86/260 patients with erectile dysfunction had venous leakage as (joint) etiology. In 5 of 86 patients cavernosography showed pathologic cavernosal drainage only via an ectopic penile vein into the femoral vein. After ligation of this pathologic draining vessel, 4 of 5 patients regained spontaneous erectability. One patient with pathologic bulbocavernosus reflex latencies needed intracavernosal injection of vasoactive drugs for full rigidity.

Zwei Patientinnen mit chronischer Hepatitis B wurden 8 bzw. 12 Wochen lang mit Vidarabin in Dosen von 1000 bzw. 700 mg/d behandelt. Am Ende der Therapie litten beide distal an den Beinen unter schweren sensiblen Reizerscheinungen; klinisch war die sensible Wahrnehmung für alle Qualitäten distal an den Beinen eingeschränkt. Drei Jahre später bestanden die Störungen weiterhin, wenn auch in milderer Form. Während kurz nach Beginn der Beschwerden die sensiblen Leitgeschwindigkeiten an den unteren Extremitäten noch nicht sicher verlangsamt waren, fand sich bei beiden Patientinnen nach einem halben Jahr eine deutliche Reduktion auf Werte unter 40 m/s für den N. suralis, die auch nach einem Jahr fortbestand. In beiden Fällen war 3 Jahre nach der Erstuntersuchung eine leichte Besserung, aber noch keine Normalisierung des elektrischen Befundes eingetreten. Der objektiv nachgewiesene lange Verlauf und die erhebliche subjektive Beeinträchtigung bei diesen Polyneuropathien sollten Anlaß zu einer sehr zurückhaltenden Indikation der Therapie mit Vidarabin sein.

The role of nucleoside triphosphates (NTPs) in the import of porin into the mitochondrial outer membrane was investigated with two forms of the porin precursor: the in vitro synthesized biosynthetic precursor (bs- porin) and a water-soluble form of porin (ws-porin) obtained by subjecting the membrane-derived porin to an acid-base treatment (exposure to trichloroacetic acid, followed by alkali and rapid neutralization). The import of ws-porin into mitochondria did not require NTPs, whereas the import of bs-porin required NTPs. In other characteristics, such as binding to a specific receptor protein on the mitochondrial surface, two-step insertion into the outer membrane, and formation of specific membrane channels, ws-porin was indistinguishable from bs-porin. Thus, the acid-base treatment applied in the preparation of ws-porin can substitute for the NTP-requiring step in mitochondrial protein import. We conclude that NTPs are required for unfolding mitochondrial precursor proteins ("translocation competent folding").

The precursors of the mitochondrial proteins ADP/ATP carrier (AAC) and F1-ATPase subunit β (F1β) were accumulated at the stages of binding to receptor sites on the mitochondrial outer membrane, or in contact sites between outer and inner membranes. Specific antibodies raised against the mature proteins were added to the isolated mitochondria and efficiently bound to these translocation intermediates. Further movement of the precursors to consecutive steps along their import pathway was thereby inhibited. Controls showed that precursor proteins which were inserted into or translocated across the outer membrane were not recognized by the antibodies unless the mitochondrial membranes were disrupted. We conclude that the trapped translocation intermediates have antigenic sites exposed to the outside of the outer membrane.