Wick technique in subscleral and subconjunctival Ologen™ implantation with trabeculectomy in patients with high risk of failure

Introduction: Ologen™ is traditionally placed subconjunctivally during trabeculectomy, which limits its area of action. Subscleral implantation of Ologen has been described involving fashioning a gutter beneath the scleral flap. This, however, would not prevent fibrosis at the margins of the scleral flap. We describe a modified technique of Ologen® placement that has the potential to prevent scarring at the margins of the flap withoutthe need to fashion a gutter. Materials and methods: The study involved a retrospective review of patients who had undergone trabeculectomy with Ologen implantation by the wick technique between January 2015 and August 2016. Patients judged to be at high risk of trabeculectomy failure were operated with this technique. Results: A total of six patients with median age of 38.5 years were included in the study. The mean preoperative intraocular pressure (IOP) was 30.8 ± 7.3 mmHg, which reduced to 10.6 ± 2.2 mmHg 18 months after surgery. By 18 months postoperative, all patients had IOP in the low teens (two patients required additional topical medication). One patient had two episodes of hypotony that responded to steroids and cycloplegics. Another patient required two needlings to bring IOP under control. No other complications were noted. Ultrasound biomicroscopy done 3 months after surgery showed two pieces of Ologen in one patient. Conclusions: The results of our study show that this technique may be used effectively in patients at high risk of trabeculectomy failure. Further studies in a larger number of patients with diverse high-risk conditions are required before this technique is recommended for general use.

Isolation of interstitial fluid from skeletal muscle and subcutis in mice using a wick method

Until recent years, mice were sparsely used in physiological experiments, and therefore, data on the basic cardiovascular parameters of mice are lacking. Our aim was to gain access to interstitial fluid and thereby study transcapillary fluid dynamics in this species. Using a modified wick method, we were able to isolate interstitial fluid from subcutis and skeletal muscle in mice. Three-stranded, dry, nylon wicks were inserted post mortem in an attempt to avoid local inflammation and thus eliminate protein extravasation and wick contamination. Colloid osmotic pressure (COP) was measured with a colloid osmometer for submicroliter samples and averaged (means ± SE) 18.7 ± 0.4 in plasma, 9.1 ± 0.4 in subcutis, and 12.3 ± 0.5 mmHg in muscle. HPLC of plasma and wick fluid showed similar patterns except for some minor peaks eluting in the <40-kDa region. Plasma protein extravasation as determined by 125I-labeled human serum albumin showed that contamination of wick fluid by plasma proteins was negligible (<2%). Capillary hyperfiltration induced by intravenous infusion of saline (10% of body wt) was reflected in tissue fluid isolated by wicks as shown by the average postinfusion COP values of 14.5 ± 0.6, 6.8 ± 0.3, and 7.7 ± 0.4 mmHg in plasma, subcutis, and muscle, respectively. We conclude that the wick technique can be easily adapted for use in mice and may represent a reliable method to isolate interstitial fluid and study transcapillary fluid flux in this species.

Isolation of pulmonary interstitial fluid in rabbits by a modified wick technique

Interstitial fluid protein concentration (Cprotein) values in perivascular and peribronchial lung tissues were never simultaneously measured in mammals; in this study, perivascular and peribronchial interstitial fluids were collected from rabbits under control conditions and rabbits with hydraulic edema or lesional edema. Postmortem dry wicks were implanted in the perivascular and peribronchial tissues; after 20 min, the wicks were withdrawn and the interstitial fluid was collected to measure Cprotein and colloid osmotic pressure. Plasma, perivascular, and peribronchial Cproteinvalues averaged 6.4 ± 0.7 (SD), 3.7 ± 0.5, and 2.4 ± 0.7 g/dl, respectively, in control rabbits; 4.8 ± 0.7, 2.5 ± 0.6, and 2.4 ± 0.4 g/dl, respectively, in rabbits with hydraulic edema; and 5.1 ± 0.3, 4.3 ± 0.4 and 3.3 ± 0.6 g/dl, respectively, in rabbits with lesional edema. Contamination of plasma proteins from microvascular lesions during wick insertion was 14% of plasma Cprotein. In control animals, pulmonary interstitial Cprotein was lower than previous estimates from pre- and postnodal pulmonary lymph; furthermore, although the interstitium constitutes a continuum within the lung parenchyma, regional differences in tissue content seem to exist in the rabbit lung.

In situ 15N labelling of lupin below-ground biomass

This paper describes the use of a cotton-wick method to enrich lupin plants with 15N. The method involved the insertion of a cotton thread through the stem and the submergence of the ends of the cotton thread in a solution of highly enriched 15N urea. The distribution of 15N in lupin plant components during pre-reproductive growth and pod filling. and in relation to the frequency of labelling, was determined. The recovery of applied 15N within plant tissues was close to 100% for lupins grown in solution culture, but 15N was not distributed between plant components in the proportions observed for total plant N. Stems and leaves were preferentially labelled with 15N irrespective of the phase of lupin growth when the 15N was applied. Pre-reproductive and mature lupin root biomass was depleted in 15N because of the poor assimilation of 15N within lupin nodules. More applied 15N was found in the root biomass of lupin plants that received fortnightly, compared with weekly, applications of 15N. The distribution of 15N between lupin components was reproducible when 15N-urea was wick-applied to plants of the same age. Recovery of 15N was incomplete when urea was fed to lupins grown in sand culture. Incomplete recovery of root material and loss of 15N associated with root exudates probably contributed to the lower recoveries of 15N in root material in sand compared with solution culture. The ability to manipulate the 15N solution concentration, the volume of solution fed to plants, time of application, and frequency of 15N application underscore the usefulness of the wick technique to label woody legumes with 15N.