Reliability of sensitivity testing of primary culture of acute dentoalveolar abscess

The antibiotic susceptibility of 50 acute dentoalveolar abscesses was determined by testing of primary cultures of pus and secondary cultures of individual isolates, using a comparative disc method. The sensitivity report obtained by primary testing agreed with that of secondary tests for 47 (94%) of the abscesses studied. It is concluded that primary testing of pus samples aspirated from acute dentoalveolar abscess is reliable and can provide the clinician with antibiotic sensitivity results more rapidly than conventional secondary testing, especially when slow-growing anaerobes are involved.     

Demonstration of increased proteoglycan turnover in cartilage explants from dogs with experimental osteoarthritis

The turnover of proteoglycans (assessed by the release into the medium of newly synthesised [35S]-proteoglycan) in explant cultures of articular cartilage from various anatomical sites of the knee joints (stifle) of mature beagles with experimental osteoarthritis has been studied with the following findings: (a) The proportion of newly synthesised proteoglycans released from cartilage explants maintained in vitro was generally increased for cartilage from operated compared with nonoperated control joints. (b) At 3 weeks after surgery there was a significant increase in the release of [35S]-proteoglycans from explants of the lateral and medial tibial plateaux of operated joints compared with sham-operated joints but not from other sites. On the other hand, when this comparison was made at 3 to 6 months after surgery, significant increases in the release of [35S]-proteoglycans were observed from cartilage of all anatomical areas except the patellar groove. (c) The release of [35S]-proteoglycan from cartilage explant cultures was dependent on live chondrocytes, since freeze-thawing the tissue immediately after labelling markedly reduced the release from both normal and osteoarthritic cartilage.     

Genotoxicity evaluation of the tricyclic antidepressants amitriptyline and imipramine using human lymphocyte cultures

Two tricyclic antidepressants, amitriptyline and imipramine, were evaluated for their in vitro cytogenetic effects in human lymphocyte cultures. Peripheral blood cultures from three normal healthy donors were set up for 72 hr for each of the drugs. The drugs were added at the start (72-hr exposure), 24 hr (48-hr exposure), and 48 hr (24-hr exposure) after initiation of the cultures. The concentrations evaluated at each exposure time were 50, 250, 1,000, and 10,000 ng/ml for amitriptyline and 25, 500, and 5,000 ng/ml for imipramine. The first two concentrations correspond to the plasma levels of the respective drugs after therapeutic doses. All treatments for a donor were given at the same time. Untreated cultures served as controls for the baseline frequency of the parameters assayed. The parameters assayed were chromosome aberrations, mitotic index, and sister chromatid exchanges (SCEs). Amitriptyline was found to be nongenotoxic at plasma levels by all the parameters assayed. However, frequencies of chromosome aberrations and SCEs were significantly increased at concentrations 4 and 40 times the plasma level (1,000 and 10,000 ng/ml) although the actual increases was small. The mitotic index was not affected at any concentration. Through imipramine showed a significant increase in chromosome damage at the upper plasma level and at concentrations higher than that, SCE frequency was significantly increased only at concentration higher than the plasma level (5,000 ng/ml), the actual increase being small for both these parameters. The mitotic index was not affected at any concentration. These results suggest that amitriptyline may be a slightly safer drug than imipramine from a genetic point of view.     

Circadian changes in PACAP type 1 (PAC1) receptor mRNA in the rat suprachiasmatic and supraoptic nuclei

A receptor for pituitary adenylate cyclase activating polypeptide (PACAP), denoted as PAC₁, is expressed in the suprachiasmatic nuclei (SCN). Since the circadian clock demonstrates phase-dependent sensitivity to PACAP, we have used in situ hybridization histochemistry to examine whether PAC₁ mRNA is differentially expressed in the rat SCN across the 24-h cycle. There was a significant variation in PAC₁ mRNA within the SCN and supraoptic nuclei during the light–dark cycle and in constant darkness, with peaks at the middle of both the real and subjective day and night; no significant variation was observed in the cingulate cortex. The results suggest that the phase-dependent actions of PACAP on the clock may involve phase-specific changes in the availability of PAC₁ receptors within the SCN.     

The effect of frequency and mean airway pressure on volume delivery during high-frequency oscillation

The performance of a commercially available oscillator (SensorMedics 31 00) at different frequencies was assessed. A frequency response curve of a pneumotachcgraph system was constructed and this was used to measure the volume delivered by the oscillator to a lung model. The volume delivered by a constant diaphragm displacement was demonstrated to be inversely proportional to the frequency, but unaffected by increasing mean airway pressure from 15 to 25 cm H₂O. The volume delivered during high frequency oscillation (HFO) was then asessed in 8 infants, median gestational age 29 weeks. The infants were studied at two frequencies, 10 and 15 Hz, both of which were used at two levels of mean airway pressure (MAP): 2 and 5 cm H₂O above the MAP level previously used during conventional ventilation. The delivered volume was not significantly different at the two MAP levels, but was significantly greater at 10 than 15 H t at both MAP levels (P < 0.03); at MAP +2 cm H₂O above baseline the reduction in delivered volume was from a median of 1.54 mL/kg (range, 0.88–3.12) at 10 Hz to 1.18 mL/kg (range, 0.6545) at 15 Hz. These results suggest that higher frequencies would require an increase in the oscillator displacement if effective gas exchange is to be maintained. © 1993 Wiley-Liss, Inc.     

Glial fibrillary acidic protein synthesized in vitro using messenger RNA from Jimpy mouse spinal cord

Glial fibrillary acidic (GFA) protein was synthesized in vitro in a rabbit reticulocyte lysate system programmed with messenger RNA (mRNA) extracted from Jimpy mouse spinal cord. It was identical in molecular weight and charge to that synthesized from normal mouse mRNA and GFA protein extracted from normal mouse cord. These data suggest that the Jimpy mutation does not affect the primary phenotypic expression of GFA protein.     

Effects of liver ischemia on hepatic protein synthesis in vitro and in vivo

When an in vitro system is used to study the influence of ischemia on hepatic protein synthesis, an important question is whether alterations observed in vitro reflect changes in vivo. In the present study the effects of liver ischemia on protein synthesis were investigated in rats both in vitro and in vivo. Liver ischemia was induced by hepatic artery ligation. Protein synthesis in vitro was determined from leucine incorporation into proteins in liver slices incubated in a medium containing ¹⁴C-leucine (0.5 mmol/l) and in vivo from leucine incorporation into hepatic proteins after intraportal injection of a tracer dose of ¹⁴C-leucine. Leucine incorporation rate in non-ischemic liver was 0.16 pmol * g pror¹ h-¹ in vitro and 19.6 μmol g prot-¹. h^-1 in vivo. After hepatic artery ligation protein synthesis in vitro was reduced by about 60% and in vivo by about 80%. Thus, the relative changes were of the same magnitude in vitro and in vivo. This indicates that an in vitro system can be used to evaluate the effects of liver ischemia on hepatic protein synthesis.     

The effects of guanethidine, bretylium and debrisoquine on the accumulation of noradrenaline in constricted postganglionic sympathetic nerves in vitro

The accumulation of noradrenaline proximal to a constriction applied to cat hypogastric nerves in vitro has been studied in preparations treated with bretylium, guanethidine and debrisoquine. All three drugs reduced the accumulation of the amine. This was paralleled by a decrease in the accumulation of dense vesicles seen with the electron microscope. Evidence is presented which suggests that the drugs e xert a noradrenaline-depleting action upon the amine-storage vesichles. At leat 18 hrs' treatment with bretylium and debrisoquine were necessary before the amine-depleting action of these drugs was evident. It is suggested that the method employed is of value in the correlation of the ultrastructural and biochemical effects of drugs on sympathetic nerves.     

The use of Percoll gradients for the preparation of subpopulations of human spermatozoa

Centrifugation of human spermatozoa on BWW- or HEPES-Krebs-Ringer-buffered media containing Percoll as a method to prepare pure gamete populations or subpopulations has been studied in detail. Application of this technique (Gorus & Pipeleers 1981) allowed us to obtain uncontaminated, motile spermatozoa and, after a subsequent Percoll gradient step, resulted in the enrichment of motile cells able to readily penetrate in vitro into AB-serum filled capillaries. The gradient sedimentation patterns of 25 different sperm samples with normal seminal parameters were found to be strongly influenced by the characteristics of the sample itself and also by the buffer used for filtration. However, the present study also revealed that ultrastructural changes and the release of intraspermatozoal enzymes were induced by the procedure. It is concluded that, although of interest clinically, the Percoll filtration technique in its present form is probably of limited value for cell biological and/or ultrastructural studies.     

On the use of monocrystalline antimony pH electrodes in gastro-oesophageal functional disorders

Monocrystalline antimony electrodes have been shown to be suitable for thein vivo determination of pH in blood, tissue and in the upper gastro-intestinal canal. Thanks to their small dimensions it has been possible to mount them into conventional manometry catheters for oesophageal investigation. The monocrystalline antimony pH electrode has several advantages over the conventional pH glass electrode; better accuracy, shorter rise time, smaller dimensions. The monocrystalline antimony electrode has been used for long-term registration of gastro-oesophageal reflux, for the oesophageal acid clearing test and for identification of the pH gradient zone between the gastric and oesophageal mucosa. Its use in combination with pressure sensors has added a new dimension to the diagnosis of functional disorders in the gastro-oesophageal region.