Hypothesis testing and anomaly explaining.

An experimenter who tests a hypothesis and observes an anomaly that conflicts with his knowledge and views, normally reacts by suspecting some sort of mistake. When he has excluded this possibility, his second sensible reaction is to find an ad hoc interpretation to explain the anomaly. When his favorite interpretation is interesting, probable, simple, elegant and testable enough, he can experiment to verify this explanation as a new hypothesis, independently from the anomaly. This article describes how a scientific investigation walks on two legs: one leg of hypothesis testing and a second leg of anomaly explaining.

Magnetic resonance imaging of male and female genitals during coitus and female sexual arousal.

OBJECTIVE: To find out whether taking images of the male and female genitals during coitus is feasible and to find out whether former and current ideas about the anatomy during sexual intercourse and during female sexual arousal are based on assumptions or on facts. DESIGN: Observational study. SETTING: University hospital in the Netherlands. METHODS: Magnetic resonance imaging was used to study the female sexual response and the male and female genitals during coitus. Thirteen experiments were performed with eight couples and three single women. RESULTS: The images obtained showed that during intercourse in the "missionary position" the penis has the shape of a boomerang and 1/3 of its length consists of the root of the penis. During female sexual arousal without intercourse the uterus was raised and the anterior vaginal wall lengthened. The size of the uterus did not increase during sexual arousal. CONCLUSION: Taking magnetic resonance images of the male and female genitals during coitus is feasible and contributes to understanding of anatomy.

In vitro and in vivo comparison of creams containing dithranol 0.5%.

In an in vitro model, the release and penetration through a silicon membrane of different cream formulations and ointments containing 0.5% dithranol were studied. The results indicated that the method is not suitable for predicting in vivo release and penetration. Experiments with rabbits showed that the degree of skin irritation produced by a hospital-prepared product containing 0.5% dithranol was comparable to that of of a commercial product. Clinical efficacy and side-effects of these two products were investigated in a double-blind left-right comparative study in 35 patients with chronic plaque psoriasis. The two creams proved to be equally effective and showed the same incidence of side-effects.

[The treatment of psoriasis in a day care center]. / Behandeling van psoriasis in een dagbehandelingscentrum.

We describe the treatment of 196 patients with psoriasis, in the psoriasis day care centre at Ede. Treatments involve salt water baths followed by radiation of UVB, additional radiation of the scalp and therapy-resistant parts of the skin and anthralin 'short contact therapy'. During the anthralin therapy the hairy scalp is treated with liq. carb. dexerg. 5% in soya oleum. The results were evaluated by means of the psoriasis area and severity index (PASI) and of a questionnaire which was completed by 144 patients. In an average course of 28.4 treatment sessions (range 9-51), the PASI decreased by 84.3%. Evaluation of the PASI included the hairy scalp, the axillae and the inguinal region. The answers to the questionnaire indicated a risk of rather rapid relapse however, according to many patients, only a small part of the skin surface was affected. The additional value of the treatment is attributed to the setting of the psoriasis day care centre and the relatively safe therapeutic possibilities offered there.

The van Andel transparent glass microsurgical cannula.

We present a disposable 21-gauge transparent glass cannula that provides optimal visual control of aspiration-irrigation procedures in cataract surgery. It is especially useful in iris coloboma repair.

Glass-metal keratoprosthesis: light and electron microscopical evaluation of experimental surgery on rabbit eyes.

A keratoprosthesis (KP) is the last and only surgical resort to regain some visual acuity in eyes with severely damaged corneae. Corneal blindness represents an important percentage of the blind in the economically poor countries. Commercially available KP's, e.g. those made of PMMA, which are difficult to sterilize and vulnerable to surface damage, are too expensive in these countries. To overcome these disadvantages, we developed a new KP, made of a glass core melted into a platinum cylinder with flange. They were implanted unilaterally in eyes of ten Hollander rabbits intralamellarly. They were fixated by two stainless steel traction threads passed around the whole eyeball. We investigated this type of KP in the rabbit cornea, its acceptance by stroma, epi- and endothelium, and its hydro-mechanical dynamics in situ. No signs of infection or extrusion were observed. No epithelial downgrowth, nor adverse tissue reaction could be detected. LM and SEM showed endothelialization of the newly formed stroma around the central column of the KP. We conclude that this type of KP (although optically still to be optimized) has been accepted by the rabbit cornea and a clinical trial on cornea-blind patients is justified.

Stainless steel as suturing material in human- and rabbit corneas: a SEM-study.

Stainless steel wire, dia. 50 microns, was used as suturing material in rabbit corneas for periods of 1.5, 3 and 7 months respectively, in order to test its inertness and acceptance by the corneal tissue. One clinical case of stainless steel wire used for fixation of an I.O.L.-implantation, after a 5-year residence in the eye, is reported as well. After 1.5 months' residence, the suture margins were well covered with tissue containing irregularly shaped endothelial cells, some fibroblastic-type cells and various kinds of collagenous fibre material. The buckled surface was partly covered with a very thin membrane of collagenous material, strands of collagenous fibres and a few fibroblastic-type cells. After 3 months' residence the buckle was almost completely covered with an endothelial cell layer. The individual cells had a somewhat irregular hexagonal shape. At a few local sites closure was still progressing, with filopodia and other collagenous matter generated by neighbouring cells on top of previously deposited Descemet's membrane. After 7 months' residence, the buckle was completely covered with normal endothelium. The fixation suture in the human case showed perfect acceptance by the corneal tissue.

A SEM-study of a keratoconus and an artificially aged human cornea.

The substructure of both the epithelial and endothelial surfaces of a keratoconus and an artificially aged cornea was compared with that of a healthy cornea by investigating them with a scanning electron microscope. From the depressions around the protruding centre of the epithelial surface of the keratoconus cornea, and from the whole epithelial surface of the artificially aged cornea, cells detached themselves, assuming a more or less rounded shape. The endothelial surface of both the keratoconus and the aged cornea showed areas of cells with an almost completely disintegrated cell membrane, exposing the cell contents. On the endothelial surface of the keratoconus cells were found with a missing cell-nucleus and a perforated cell membrane, due to a 'Kammerwasser Einbruch' effect.

A keratoprosthesis successfully implanted in the cornea of a rabbit, a SEM-study.

By means of a new fixation technique keratoprostheses were fixed in the cornea of 'Hollander' rabbits. The fixation is based on the use of corneo-sclerally orientated stainless steel-vanadium traction threads in corneal stroma and scleral tissue. Keratoprostheses placed according to this fixation technique have a follow-up of a maximum of two years. The liquid sealing capacity, the cell behaviour on the surface of the prosthesis and the anchoring of the stainless steel vanadium wire have been investigated in detail with the scanning electronmicroscope (SEM).