Subtemporal decompressions for shunt-dependent ventricles: mechanism of action

The literature suggests that subtemporal decompression is an effective treatment for the syndrome of shunt-dependent ventricles because it allows the ventricle to enlarge around the shunt catheter tip. Pre- and post craniectomy ventricular areas were measured from computed tomography scans with a computer digitizing technique in three patients with this syndrome who had undergone four surgical procedures. All patients improved symptomatically following craniectomy. A significant decrease in total ventricular area was noted in all instances. The results suggest that subtemporal craniectomy causes the ventricles to become smaller, not larger. Other possible explanations for the effectiveness of the procedure are discussed.

[Psychiatric problems in therapy with benzodiazepines]

Attractive characteristics of benzodiazepines are their efficiency in reducing anxiety and nervous tension and their safety as to serious side effects and intoxication. Although not producing tolerance, they can lead to dependence. Withdrawal symptoms may occur after long-term use even of therapeutic doses. Their effectiveness in alleviating many states of distress and even common lack of well-being may lead to abuse both for the patient, who puts off the necessary problem-solving, and for the physicians by inducing them to medicalize trivial life-crises. The indication for the use of benzodiazepines should therefore be restricted and prescription limited to short-term administration.

Inhibition by dipyridamole of cerebral vasospasm induced in vitro by whole blood

This study evaluates the effect of dipyridamole, an inhibitor of platelet aggregation, on cerebral artery contraction induced in vitro by the addition of whole blood. Whole fresh arterial blood added to isolated rabbit basilar artery bathed in a physiological buffer produces a sustained contraction in vessels observed for 60 minutes. Significant dose-dependent inhibition of contraction was observed when dipyridamole was added to the vessel bath. This effect was not influenced by preincubating cerebral vessels with aspirin, an inhibitor of prostaglandin synthesis. It is suggested that inhibition of whole blood-induced cerebral artery contraction by dipyridamole does not result from potentiation of cerebral vessel prostaglandin pathways, but possibly from a direct effect on platelets.

Functional improvement after spinal surgery for the dysraphic malformations

Spinal surgery for the various dysraphic malformations is generally indicated to arrest disease progression. The results of the present study suggest that certain clinical conditions and presentations are associated with an exceptionally good surgical prognosis. Sixty-nine procedures were done in 55 patients. The diagnoses included hydromyelia and tethered cord related to diastematomyelia, lipoma, lipomeningocele, previous operation, and thickened filum terminale. The operative results were evaluated for significant functional neurological and urological improvement, as well as for the relief of pain. Pain relief was achieved in 92% of patients with preoperative pain. Significant functional return was seen in 67% of hydromyelia patients. On the other hand, surgical treatment of tethered cord caused improvement in 24% (lipoma) to 46% (thickened filum and diastematomyelia). These results suggest that patients with hydromyelia and patients with a dysraphic malformation and pain have an excellent prognosis after operation. A re-evaluation of the indications for surgery for these patients may be necessary.

Immunochemical analysis of high molecular mass urinary proteins

Urinary high molecular mass proteins (fraction P) solubilized in Triton X-100 and by papain have been compared with the solubilized human renal brush border membrane proteins. Crossed immunoelectrophoresis of Triton X-100 fraction P extract, by means of two polyspecific antisera directed against either renal membrane or fraction P, revealed eleven immunoprecipitates antigenically identical with detergent renal membrane antigens. Among them, five hydrolases were identified by zymogram staining: microvillus aminopeptidase, maltase, trehalase, gamma-glutamyltransferase and alkaline phosphatase. Eight papain-solubilized fraction P proteins and Triton X-100-solubilized membrane extract presented 'identity' patterns in tandem crossed immunoelectrophoresis, but differed in their amphiphilicity, as demonstrated by the change of precipitation pattern on charge-shift caused immunoelectrophoresis. Among the eleven detergent-solubilized fraction P antigens, nine were proved to be amphiphilic proteins and six presented bidirectional charge shifting properties similar to those of renal membrane antigens. Quantitatively, five detergent fraction P proteins were found in the same amounts as in renal membrane extract, two in lesser amounts and four in greater. Moreover, the same two plasma proteins were identified in fraction P as in the renal membrane. Thus important similarities exist between the urinary fraction P and the native renal membrane.

[Urinary elimination of multiple forms of gamma-glutamyltranspeptidase and aminopeptidase (author's transl)]

Concentrated and dialyzed 24-h urines of healthy persons were separated by 105000 X g ultracentrifugation into a pellet (P105) and a supernatant (S105) fraction. Chromatography of the P105 fraction on Sepharose 4B and 2B revealed that gamma-glutamyltranspeptidase and aminopeptidase activities had a molecular mass of 20 X 10(5) to 40 X 10(6), whereas in the S105 fraction soluble gamma-glutamyltranspeptidase and aminopeptidase had 86000 and 160000, respectively. Triton X-100 solubilization was performed on the P105 fraction and on a human renal cortex 40000 X g pellet, used as a reference. All the activity was recovered in both cases in a single peak of detergent gamma-glutamyltranspeptidase and detergent aminopeptidase eluted by filtration on Ultrogel Ac A22. Apparent molecular mass of Triton X-100 solubilized urinary and renal enzymes were 250000 and 243000 for gamma-glutamyltranspeptidase, and 298000 for both aminopeptidases. Protease solubilized forms were obtained by trypsic digestion of detergent urinary and renal forms. Both gamma-glutamyltranspeptidases were found to have an apparent molecular mass of 86000 on Sephadex G 150, which is identical to the value found for the S105 urinary gamma-glutamyltranspeptidase. The aminopeptidases had 238000 and 232000, which is a higher value than the molecular mass of the S105 urinary aminopeptidase. This letter could be a degraded form of the renal aminopeptidase. These findings suggest that gamma-glutamyltranspeptidase and aminopeptidase in the P105 fraction are similar to native renal enzymes. Evaluation of the P105 fraction enzymatic activities may thus be useful in the diagnosis of tubular damage.

Significance of postshunt ventricular asymmetries

Ventricular asymmetries after shunt surgery were studied. Right and left ventricular areas from pre-and postoperative computerized tomography scans were measured with a computer digitizing technique, and the respective areas were expressed as a ratio. Measurements were made from the scans of 15 hydrocephalic children selected at random. Ages at surgery ranged from 1 to 101 weeks. The results indicate a significantly greater decrease in ventricular size on the side of the ventricular shunt catheter. Multiple regression analysis showed no relationship between the magnitude of change in ventricular size and either the patients' age orn the time intervals between surgery and follow-up scans. Possible mechanisms for these postshunt ventricular asymmetries are discussed.

Prevention of persistent cerebral smooth muscle contraction in response to whole blood

Using an in vitro system designed to measure arterial constriction, we have demonstrated the importance of platelet function in maintaining cerebral smooth muscle contraction after whole blood injection. We tested two agents, acetyl salicylic acid (ASA) and phthalazinol, both known to interfere with platelet function. In control tests normal rabbit and monkey blood produced a reliable and persistent arterial constriction. In experimental tests blood drawn from animals premedicated with ASA and phthalazinol failed to produce a persistent contraction. These results support the hypothesis that chemicals released during platelet aggregation may be important in persistent vasospasm.

Inhibitory postsynaptic actions of taurine, GABA and other amino acids on motoneurons of the isolated frog spinal cord

The actions of glycine, GABA, alpha-alanine, beta-alanine and taurine were studied by intracellular recordings from lumbar motoneurons of the isolated spinal cord of the frog. All amino acids tested produced a reduction in the amplitude of postsynaptic potentials, a blockade of the antidromic action potential and an increase of membrane conductance. Furthermore, membrane polarizations occurred, which were always in the same direction as the IPSP. All these effects indicate a postsynaptic inhibitory action of these amino acids. When the relative strength of different amino acids was compared, taurine had the strongest inhibitory potency, followed by beta-alanine, alpha-alanine, GABA and glycine. Topically applied strychnine and picrotoxin induced different changes of post-synaptic potentials, indicating that distinct inhibitory systems might be influenced by these two convulsants. Interactions with amino acids showed that picrotoxin seletively diminished the postsymaptic actions of GABA, while strychnine reduced the effects of taurine, glycine, alpha- and beta-alanine. But differences in the susceptibility of these amino acid actions to strychnine could be detected: the action of taurine was more sensitively blocked by strychnine compared with glycine, alpha- and beta-alanine. With regard to these results the importance of taurine and GABA as transmitters of postsynaptic inhibition on motoneurons in the spinal cord of the frog is discussed.

Jet injection of insulin vs the syringe-and-needle method

A new technique of injecting insulin without a needle employs a jet injector to administer a high-pressure stream of medication. This method causes very little pain and affords great accuracy, ease of administration, and safety. The medication is more widely diffused in the body by jet injection than by the needle-and-syringe technique. The control of blood sugar (with similar doses of insulin) achieved by the two techniques is similar, and their effect on local tissues is also similar. In the patients studied, jet injection appeared to be a very satisfactory method of administering insulin and has met with good patient-acceptance. Jet injection is also a useful method for the visually handicapped.