Depression and somatosensory evoked potentials: II. Correlations between SEP and depressive phenomenology.

In 32 patients with major depressive disorders according to Research Diagnostic Criteria (RDC), symptomatology was rated using the Schedule for Affective Disorders and Schizophrenia (SADS), and somatosensory evoked potentials (SEP) elicited by tactile fingertip stimuli were recorded at the vertex of the scalp. Patients were drug-free except for benzodiazepines. Amplitudes and amplitude/stimulus intensity slopes were adjusted to same sex, age, height, and weight. Uni-and multivariate correlations revealed associations between the N140-P200 amplitude and hypothyroidlike aspects of depression with symptoms such as poor appetite and indecisiveness, and between the P100-N140 slope and intrapunitive aspects of depression with symptoms such as negative self-evaluation and suicidal attempts. Neither attention level nor benzodiazepine medication were reflected in these relationships.

Depression and somatosensory evoked potentials: I. Correlations between SEP and monoamine and purine metabolites in CSF.

In 32 patients with major depressive disorders diagnosed according to Research Diagnostic Criteria (RDC), somatosensory evoked potentials elicited at four levels of tactile fingertip stimulation were recorded. Four peak-to-baseline amplitudes (P100, N140, P200, and P300) and two peak-to-trough amplitudes (P100-N140 and N140-P200) plus their amplitude/stimulus intensity slopes were selected for analysis. All 12 measures were adjusted to same sex, age, height, and weight. Values were linearly and curvilinearly correlated with adjusted levels of homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5HIAA), 3-methoxy-4-hydroxyphenylglycol (MPHG), hypoxanthine, and xanthine in the cerebrospinal fluid (CSF), monoamine and purine metabolites, respectively. Significant negative linear correlations were found between the P300 amplitude and both HVA and hypoxanthine, and between the P200 slope and both 5HIAA and hypoxanthine. A significant positive correlation existed between the N140-P200 slope and 5HIAA. Curvilinear bivariate regressions demonstrated complex topologies of regression surfaces. Neither attention nor benzodiazepine medication were of significant importance in these relationships.

Influence of capillary multifilament sutures on the antibacterial action of inflammatory cells in infected wounds.

Implants of two capillary multifilament suture materials, braided polyester and twisted polyamide with cover, in tissue infected with Staphylococcus aureus were studied with light microscopy and transmission electron microscopy. In the tissue around both suture materials there was a pronounced inflammatory cell reaction. Staphylococci were found between the filaments of both materials. Some ingrowth of granulation tissue with inflammatory cells close to the exterior thread surface was seen in braided polyester suture. No such infiltration was seen in the suture consisting of twisted polyamide with cover. Bacteriologic studies showed faster elimination of staphylococci from the braided polyester than from the twisted polyamide implants. The capacity of leukocytes to penetrate into a capillary multifilament material presumably is dependent on the structure of the suture thread. Bacteria which are enclosed in the interstices of multifilament suture material, and protected from the phagocytic activity of leukocytes, can sustain and prolong an infection.

Enclosure of bacteria within capillary multifilament sutures as protection against leukocytes.

The effect of leukocyte against Staphylococcus aureus in the presence of capillary multifilament suture materials was observed in an in vitro phagocytosis test. The leukocytes had a phagocytic effect against bacteria in the culture medium but not against bacteria in the suture threads. The bacteria enclosed in the interstices of the suture threads could multiply there, and 'leakage' of bacteria from the thread to the surrounding medium maintained a high bacterial presence despite the phagocytic activity of leukocytes in the medium. Adherence of leukocytes to suture materials was studied in experiments with 51Cr-labeled leukocytes. There was no significant leukocyte penetration into the two capillary multifilament suture materials in the tests. Bacteria enclosed in the interstices of capillary multifilament suture threads appear to be protected from the phagocytic action of leukocytes and thus can support and prolong the course of an infection.

Microbiological evaluation of suture items before radiation sterilization.

Microbiological contamination levels of suture samples taken at various stages of the manufacturing process in a new hygienically controlled plant were determined by employing a membrane filturation technique. Both raw material and materials handled manually in the production process were tested to assess the effect of manual handling on the product contamination level. Evaluation of the efficacy of contamination control, however, was directed primarily to the finished, packaged products, just prior to the processing with cobalt 60. The suture material for testing was divided into two groups, namely, wet and dry products, the wet being packaged in a special "tubing" fluid consisting mainly of isopropyl alcohol. Initial contamination results are reported as the average of values obtained on the test day and the preceding 9 consecutive production days. A total of 1,787 suture samples tested in the dry group showed daily averages varying between 2.1 and 14.8 contaminants per suture. The 2,980 wet-packaged suture samples tested gave daily averages varying from 0.7 to 4.2 contaminants per suture. The highest values obtained for an individual suture were 400 for the dry and 89 for the wet. Identification studies of the contaminants revealed that fungi predominated. Most of the bacterial contaminants proved to be spore-forming rods.

Fluid absorption and capillarity of suture materials.

The fluid absorption and capillarity of different suture materials commonly used were investigated in saline and blood plasma. Linen and silk have high fluid absorption in plasma (92.2 +/- 1.3%, 65.2 +/- 0.7% of dry weight), and polyamide twisted with cover together with polyester considerably lower absorption (27.0 +/- 0.8%, 16.0 +/- 0.3%). Monofilament polyamide has fluid absorption ability in spite of its homogeneous structure (10.1 +/- 0.2%). Capillary properties were demonstrated in all multifilament synthetic and natural materials but were effectively eliminated by waxing treatment. The fluid transport rate constant varied considerably between different materials and was highest for polyamide with cover. Fluid absorption and capillary properties are presumed to be of significance for the impact of contaminating bacteria.

Effect of suture materials on bacterial survival in infected wounds. An experimental study.

A non-capilllary and a capillary suture material were compared as regards the course of Staphylococcus areus infection at the site of implantation. The materials were implanted in the muscle of the rat, and bacterial counts were made at intervals over 41 days. The number of bacteria recovered at the implantation site during the test period decreased steadily and was significantly lower for the non-capillary than for the capillary materials. In the latter case the bacterial counts did not fall far below the initial value at inoculation. The number of bacteria isolated from the suture thread in relation to the total number from the thread and the surrounding muscle was significantly greater for the capillary material. The difference in the results for the two types of suture materials might be ascribed to differences in the extent to which the bacteria are exposed to the body's defence mechanism; in the case of the capillary suture material the bacteria would tend to be protected through their enclosure in the interstices of the material.

Suture material and bacterial transport. An experimental study.

The transport of bacteria and spreading of infection by suture materials was studied. An in vitro experiment showed that immobile bacteria can propagate inside multifilament materials. The spreading was correlated to the capillary properties of the threads. A similar result was obtained in an in vivo study in the muscle of the rat. The bacterial transport inside the thread was found to be of significantly greater importance for the spreading of wound infection than that on the surface of the material.