FSBA modifies both alpha- and beta-subunits of F1 specifically and can be bound together with AXP at the same alpha-subunit.

Binding of 1 mole 5'-fluorosulfonylbenzoyladenosine (FSBA) per mol F1 induces about 50% inhibition of ATPase activity and 80% inhibition of ITPase activity. The binding of additional ligand results in a further inhibition of both activities. Maximally 5 mol/mol F1, causing complete inhibition of activity, can be bound. Using radioactive FSBA more label is found on alpha-subunits than on beta-subunits under the usual buffer conditions. The modified amino acids are alpha-Tyr300, alpha-Tyr244 and beta-Tyr368. Binding of FSBA, at least up to 3 mol/mol F1, does not result in loss of bound ADP, whether the starting enzyme contains 2, 3 or 4 bound nucleotides. Added adenine nucleotides compete with FSBA only for binding that results in modification of beta-subunits, shifting the alpha/beta ratio of bound label to higher values. It is concluded that the alpha-subunits contain two hydrophobic pockets for the binding of nucleoside moieties, with a different orientation relative to the P-loop. One pocket contains alpha-Tyr244 and alpha-Tyr300, the other beta-Tyr368. Since, however, in the binding of adenine nucleotide di- or triphosphates the P-loop is involved, only one of these ligands can bind per subunit. The previously not understood binding characteristics of several substrate analogues have now become interpretable on the assumption that also the structurally homologous beta-subunits contain 2 pockets where nucleoside moieties can bind. The kinetic effects of FSBA binding indicate that the first FSBA binds at the regulatory site that has a high affinity for ADP and pyrophosphate. Binding of pyrophosphate at this high-affinity regulatory site increases the Vmax of the enzyme, while binding at a second regulatory site, a low-affinity site, increases the rate of binding of FSBA with a factor of about 3. Binding of bicarbonate at this latter site is responsible for the disappearance of the apparent negative cooperativity of the ATPase activity.

Cerebrospinal fluid otorrhea treated by extended subtotal petrosectomy with obliteration.

Extended subtotal petrosectomy as a treatment for stubborn cerebrospinal fluid (CSF) otorrhea is presented. Nine patients were successfully operated on by this technique, all previously having undergone surgery for brain or base of skull lesions, other interventions used had failed to seal the fistula. The retrosigmoid cells, facial cells, and internal auditory canal were found in our study to be the most commonly involved during pervious neurosurgery and so constituted the usual path for CSF leakage. Total exenteration of middle ear and mastoid cell tracts, skeletization of sigmoid sinus, jugular bulb and facial nerve, drilling out of the semicircular canals, vestibulum, and cochlea, and skeletization of the internal auditory canal are the main steps of this approach.

[Fungal infections in 2 cases of fulminant hepatitis]. / Infección por hongos en dos casos de hepatitis fulminante.

Infectious complications are highly prevalent in patients with fulminating hepatitis. We report 2 female patients, aged 42 and 80 years old, with fulminating hepatitis caused by virus B and virus non-A non B, who died 20 and 25 days after initiation of the disease. Post mortem examinations showed severe C albicans infection of the gastrointestinal tract. A literature review is included.