Effect of electrophilic and nucleophilic substituents on the protonation microequilibria of tyrosine derivatives

The microscopic protonation constants of 10 tyrosine-like, unusual amino acids used in the syntheses of opioid peptides have been determined by using a combined pH-metric-spectrophotometric method, at 0.10 mol dm ^?3 (NaCl) ionic strength and 25.0°. The role of the different electrophilic and nucleophilic substituents on the individual basicity of the aliphatic amine and phenolic hydroxylate basic centers is discussed in detail. The interactivity parameters between these two groups correlate fairly well with the structure of the skeleton and the distance between the two basic centers, but they were found to be substituent-independent. This finding made it possible to extend the calculations to compounds having non-overlapping protonation equilibria.     

Hepatic metastasis detection: comparison of three CT contrast enhancement methods

A prospective, blinded comparison of three methods of hepatic contrast enhancement in computed tomography (CT) was conducted in 15 patients with colorectal carcinoma metastatic to the liver. Arterial portography (AP-CT) was performed with injection of contrast material into the superior mesenteric artery during CT. Delayed scanning (DS-CT) was performed 4 hours after intravascular administration of contrast material (mean dose, 280 mL). CT with an ethiodized oil emulsion (EOE-CT) was performed 1 hour after slow intravenous infusion of the emulsion. All patients underwent laparotomy following imaging studies. A lesion-by-lesion analysis of 56 metastases showed no significant differences in sensitivity (AP-CT, 77%; DS-CT, 83%; EOE-CT, 82%), but the false-positive rate for AP-CT was significantly higher than that for DS-CT (P less than .001) or EOE-CT (P less than .01). False-positive rates for EOE-CT and DS-CT were not significantly different. The predictive value of a positive test was 63% for AP-CT, 90% for DS-CT, and 81% for EOE-CT. AP-CT does not appear to be clinically useful for detection of hepatic metastases because of the high false-positive rate. No difference could be demonstrated between DS-CT and EOE-CT. DS-CT is a valuable method for hepatic contrast enhancement.     

Rathke cleft cysts: CT, MR imaging, and pathologic features

The authors retrospectively reviewed the clinical, computed tomography (CT), and magnetic resonance (MR) imaging findings in seven patients with pathologically proved Rathke cleft cysts. All the cysts were located in the anterior sella turcica or the anterior suprasellar cistern. Five cysts had both intra- and suprasellar components, one was entirely intrasellar, and the other was predominantly suprasellar in location. The size of the cysts ranged from 8 to 20 mm. CT scans demonstrated low-density homogeneous lesions in four cases. On MR images of three of these four cases, the cysts had the same intensity as cerebrospinal fluid on T1- and T2-weighted images, while in the fourth case, the cyst was hyperintense on the T1-weighted images. In the remaining three cases, CT showed slight hyperdensity relative to brain parenchyma, suggestive of contrast enhancement. MR showed signal heterogeneity of these lesions with focal components of diminished signal intensity of T2-weighted images. These same foci appeared iso- to slightly hyperintense on T1-weighted images.     

Vein plasma endothelin-1 and cyclic GMP increase during coronary angioplasty is related to myocardial ischaemia

Endothelin-1 and cyclic guanosine monophosphate (c-GMP) peripheralvein plasma levels increase during coronary angioplasty, butthe reason for this increase has not been elucidated. The purposeof this study was to investigate whether these changes are relatedto myocardial ischaemia, or to mechanical artery injury inducedduring the procedure. Thirty-two patients with stable anginapectoris and a single lesion were studied. They were aged 56±8 and were undergoing balloon angioplasty. Eight arterieswere totally occluded and 24 were partially occluded. Bloodsamples were drawn from a peripheral vein after coronary arteryengagement with the guiding catheter (baseline), after the firstballoon inflation, immediately after the end of the procedure,and 4 h later.In the total occlusion group endothelin-1 increasedby 7% (P ns), whereas in the partial occlusion group it increasedby 45% after the procedure (P<0.001). c-GMP in the partialocclusion group increased by 41% (P<0.001) after the procedurewhereas in the total occlusion group it increased by 5% (P ns).Thus, the increase in endothelin-1 and c-GMP peripheral veinplasma levels after coronary angioplasty is related to myocardialischaemia rather than to mechanical artery injury.     

Ecotoxicity of 3,4-dichloroaniline in enclosed freshwater plankton communities at different nutrient levels

The sensitivity of Daphnia magna to 3,4-dichloroaniline (DCA) was studied in a multispecies mesocosm study and its response was compared to those of naturally occurring zooplankton species. A series of DCA concentrations was tested during two experiments conducted in 1.2 m3 plastic enclosures, which contained water and natural plankton from Lake Markermeer (The Netherlands) and laboratory-cultured D. magna. Low concentrations of 2.7 and 27 mu g l-1 were tested during the first experiment and additional nutrients were supplied to half of the enclosures. Cladocerans were found to be the zooplankton group most sensitive to DCA. The addition of nutrients resulted in a more marked reduction of cladoceran populations at 27 mu g l-1. In the second experiment, additional DCA concentrations (27, 90 and 270 mu g l-1) were tested under nutrient-enriched conditions only. The EC50 for D. magna, calculated from the integrated density over the first 21 days, was 3.2 (1.9--5.5) mu g l-1 DCA when the results of the two experiments were combined. Two naturally occurring dominant cladoceran species were more sensitive to DCA than was D. magna. Less sensitive rotifer and copepod species profited from the reduced competition. The opportunisitic response of the less sensitive species could not prevent an increase in phytoplankton densities at high nutrient supply. The results show that both the effects of DCA on zooplankton and the diminished control exerted by zooplankton on phytoplankton are intensified under nutrient-enriched conditions     

The prognostic value of facial nerve conduction velocity in patients with Bell's palsy

The facial nerve conduction velocity was measured in 30 healthy subjects (60 sides) and in 51 patients with a unilateral Bell's palsy. The normal value was 47.8 ± 5.1 m/s. Incomplete recovery was common in Bell's palsy when the velocity was below 30 m/s. Mild synkinesis was observed in only one patient when the nerve conduction velocity was above 30 m/s. When the degree of degeneration revealed by electroneuroneography did not exceed 60%, the conduction velocity was in the normal range. For degrees of degeneration in excess of this, the conduction velocity decreased in parallel with the increase in the degree of degeneration.     

Effect of Extracorporeal Shock Wave Lithotripsy on Prostate Specific Antigen

Purpose

We evaluated the effects of extracorporeal shock wave lithotripsy (ESWL^*) of distal ureteral calculi on serum prostate specific antigen (PSA).

Materials and Methods

A total of 29 consecutive men with distal ureteral calculi at a maximum of 25 mm. from the ureteral orifice, and without any history of urinary tract infection, benign prostatic hyperplasia or prostate cancer underwent ESWL with the Dornier MPL 9000 × lithotriptor. The therapeutic focus size was 48 × 7 mm. PSA was measured exactly 5 minutes before ESWL, as well as 120 minutes, 24 hours and 7 days after termination of treatment.

Results

Fragmentation rate was 100 percent and all patients were stone-free within 1 week of therapy. There was no statistically significant difference between PSA values before and after treatment. Only 15 patients had a slight increase in PSA at 120 minutes after treatment (range 0.01 to 0.41 ng./ml., mean 0.07).

Conclusions

ESWL can be performed in men at risk for prostate cancer without impairing the predictive value of PSA.     

Hepatosplenic candidiasis: wheels within wheels

Eight immunocompromised cancer patients with tissue-proved candidiasis underwent serial abdominal ultrasound (US) and computed tomography (CT). At US, four patterns of hepatic and splenic candidiasis were recognized, one of which the authors call a "wheels-within-wheels" pattern. In addition, periportal linear areas of increased attenuation, possibly calcified, were identified at follow-up, nonenhanced CT. Some abscesses were better seen on nonenhanced CT scans, while others became visible only with enhancement. Although lesions not seen at US were often seen at CT, the opposite was also true. In two cases, pathologic proof of candidiasis was established even when all imaging studies were normal. For maximum imaging sensitivity, patients should be studied with US and nonenhanced and enhanced CT. Even when both US and CT scans are negative, if there is a strong clinical suggestion of candidiasis, open biopsy is recommended.