Keratoacanthoma: the value of photographic follow-up in conservative management

The management of keratoacanthoma is controversial. Two cases are presented to confirm the value of conservative treatment. The presence of hairs within keratoacanthomas as a diagnostic feature is discussed. Correspondence to: R.W. Griffiths     

An unusual clinical presentation of bilateral schizencephaly

Summary We present a case with a characteristic magnetic resonance image (MRI) of bilateral open-lipped schizencephaly and atypical clinical presentation. The patient is still alive and in good health in her forties, she has never presented seizures, and although the motor dysfunction is well correlated with cerebral lobe involvement, neurobehavioral dysfunction is not proportional to the MR image of the cerebral malformation.

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Un cas inhabituel de schizencéphalie bilatérale

Résumé Nous présentons un cas de schizencéphalie bilatérale ouverte caractérisé par une présentation clinique atypique et une imagerie par résonance magnétique nucléaire caractéristique. La patiente est encore vivante, en bonne santé, à plus de 40 ans, elle n'a jamais présenté de crise comitiale et, bien que les troubles moteurs soient bien corrélés aux altérations cérébrales, les troubles neuro-comportementaux ne sont pas proportionnels aux images IRM de cette malformation cérébrale.

     

Identity of immune cells in graft-versus-host disease of the skin. Analysis using monoclonal antibodies by indirect immunofluorescence.

The cellular infiltrate in skin biopsies of 9 patients with graft-versus-host disease (GVHD) has been characterized with the use of monoclonal antibodies by indirect immunofluorescence. Most infiltrating cells in dermis reacted with monoclonal antibodies which recognize T-cell antigens. A mean of 45% of all dermal cells were T11-reactive, while a smaller proportion of cells were identified by another "pan" antibody, OKT3. In all but two instances the proportion of dermal cells reactive with OKT8 exceeded the proportion reactive with OKT4. Anti-Tac, which identifies activated T cells, reacted with a variable proportion of cells. Monocytes and null cells (OKM1+) were frequently observed but were less numerous than T-lymphocytes. Infiltrates were sparsely populated with OKT6-reactive cells, and there was no difference between the number of intraepidermal cells reactive with this antibody in study subjects and normal controls. Few cells reactive with Leu 7 (large granular lymphocytes) or with anti-B-cell reagents were seen. These findings may have clinical implications for use of monoclonal antibodies for prophylaxis and treatment of GVHD.     

Reduction of FK-506 requirements by combination with polyethylene glycol superoxide dismutase in orthotopic rat liver transplantation

Reperfusion after ischemia results in endothelial cell injury and Kupffer cell activation. Inflammatory cytokines thus released can induce major histocompatibility complex antigens and increase the immunogenecity of the graft. An orthotopic rat liver allotransplant model was used to test the hypothesis that prevention of reperfusion injury by infusion of polyethylene glycol superoxide dismutase (PEG-SOD) would result in long-term allograft survival in the presence of subthreshold immunosuppressive dosages. ACI rats were used as donors, and Lewis strain rats as recipients. Orthotopic liver transplantation was initially performed to identify a subthreshold dose of the immunosuppressant FK-506, which would be unable to extend survival longer than control untreated rats with this strain combination. After testing three intramuscular FK-506 doses of 0.04, 0.08, and 0.16 mg/kg, it was observed that an FK-506 dose of 0.04 mg/kg/day for 14 days was unable to extend survival longer than in untreated recipients. This dose of FK-506 was used in combination with PEG-SOD at doses of 1000, 3000, 10,000, or 30,000 units. Recipient animals were treated intravenously with PEG-SOD as a loading dose to facilitate tissue penetration on day 1, and beginning on the day of transplantation, every 2 days for the duration of the study. Results of histologic studies and mean survival time were compared in untreated recipients and in rats treated with PEG-SOD plus 0.04 mg/kg/day FK-506. Mean survival time was increased significantly in these animals (p < 0.007) to 40.6 ± 25.6 days as compared with either untreated rats (10.0 ± 2.7 days) or rats treated with 0.04 mg/kg FK-506 alone (13.7 ± 4.2 days). Histologic examination demonstrated a significant reduction in the cellular infiltrate in rats treated with PEG-SOD plus FK-506, as compared with recipients treated with either agent alone or left untreated. Our results therefore suggest a potential approach to reducing immunosuppression in transplantation. (J ALLERGY CLIN IMMUNOL 1995;95:1276-81.)     

Primary squamous cell carcinoma of the terminal ileum.

A case of squamous cell carcinoma of the terminal ileum with no underlying duplication or inflammatory disorder is described. The neoplasm seemed to have originated from the surface epithelium, invading the wall and metastasising to the regional lymph nodes. The 65 year old patient was free of disease three years after having had the tumour removed. Previous reports of squamous carcinoma of the small intestine have been associated with intestinal duplication or metastatic disease from distant sites.     

Characterisation of rat superficial superior colliculus neurones: firing properties and sensitivity to GABA

Physiological, pharmacological and morphological properties of superficial superior colliculus neurones (n=93) were characterised using whole-cell patch-clamp recordings in rat brain slices. Six cell types (narrow- and wide-field vertical, horizontal, piriform, marginal and stellate) were identified based on Lucifer Yellow labelling but no cell type-specific spike pattern could be identified. Resting membrane potentials were homogeneous (mean: -67.1 +/- 0.7 mV, n=48), and spike frequencies ranged from 10 to 70 Hz (80 pA current injection). About 66% of the cells displayed regular and sustained spike production, throughout all neuronal categories. Rebound spikes and spontaneous activity were observed frequently in all cell types. Synaptically evoked action potentials appeared as single spikes (mean amplitude: 76.0 +/- 3.2 mV, n=34) followed by a fast after-hyperpolarising potential (mean amplitude: 25.4 +/- 1.4 mV, n=34) and variable late potentials (late after-depolarising and/or -hyperpolarising). Pharmacologically, a characterisation using GABA and its subtype-specific agonists indicated a strong inhibitory influence of this transmitter system on >90% of cells. The GABA(A) receptor agonist, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (100 microM), caused a reversible hyperpolarisation (approximately 9 mV) and spike inhibition of all neurones studied. This was more pronounced for intrinsic than for synaptically evoked spikes. Assessment of the GABA(C) receptor agonist, cis-4-aminocrotonic acid (1 mM), also revealed a hyperpolarisation (approximately 3 mV) and an inhibitory action on firing, but this was not as potent and homogeneous, compared to the GABA(A) receptor agonist. Further, the GABA(B) receptor agonist, baclofen (50-100 microM), had more variable (hyperpolarising, depolarising or no change) effects on the membrane potential. It showed little modulation of current-induced action potentials but fully blocked synaptic spikes. Assessment of GABA receptor antagonist actions revealed the presence of weak tonic and strong phasic GABA(A) receptor-mediated inhibition in the superficial superior colliculus: application of the GABA(A) receptor antagonist, bicuculline (100 microM), led to a generally enhanced excitability and depolarisation (approximately 5 mV). Intrinsic firing was somewhat enhanced, but synaptic spiking was drastically potentiated and prolonged. In contrast, 1,2,5,6-tetrahydro-(pyridin-4-yl) methylphosphinic acid (TPMPA; 100 microM), the GABA(C) receptor antagonist, produced little effect on these physiological parameters. The GABA(B) receptor antagonist, CGP35348 (200 microM), caused a partial inhibition of late after-hyperpolarising potentials (approximately 30%). Uptake of GABA contributes little to endogenous inhibition in the superior colliculus slice preparation, as suggested by the action of GABA uptake inhibitors SKF89976 (50-100 microM) and nipecotic acid (200-500 microM), both had no obvious effect on physiological parameters. However, in the presence of these compounds, sub-maximal inhibitory actions of GABA were potentiated.In conclusion, different cell types in the superficial superior colliculus do not display distinct physiological properties and are subject to strong inhibitory modulation. We therefore suggest that signal processing in this brain region does not require cell type-specific encoding of information. In line with evidence provided by previous in vivo investigations, identification of visual stimuli and orientation responses appears to be realised via the network properties of the receptive fields that form topographic maps.     

Mechanical properties of four methylmethacrylate-based resins for provisional fixed restorations

The use of a provisional restoration is an important phase in the treatment of the dental prosthetic patient. A good provisional restoration should satisfy the following requirements: pulpal protection, positional stability, ease in cleaning, accurate margins, wear resistance, dimensional stability, and serve as a diagnostic aid in treatment assessment and esthetics. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnecessary repair. Heat-processed and reinforced methacrylate-based resins have been used to improve the mechanical and physical properties of provisional restorations. Among various improvements, the interpenetrating network crosslinked PMMA (IPN) has been shown to have superior mechanical properties if manufactured through a dough compression molding process at 130 degrees C. However, there have been no published data that relate with the use of this material for fixed provisional restorations.The objective of this study was to compare four methyl methacrylate-based resins for provisional crowns and bridges with varying processing cycles, including JET [self-cure], ACRALON [heat-cured], titanium dioxide filled PMMA [heat-cured], and IPN [heat-cured denture tooth resin]. Properties studied included transverse strength, toughness, rigidity, and hardness. From the results of this study the following conclusions can be made: the IPN group may have had a lower degree of conversion as demonstrated by decreased strength, toughness, and hardness data as compared with Acralon. Increasing the polymerization cycle of unmodified Acralon resin causes a significant increase in strength.     

Apoptotic cell death in mouse models of GM2 gangliosidosis and observations on human Tay-Sachs and Sandhoff diseases

Tay-Sachs and Sandhoff diseases are autosomal recessive neurodegenerative diseases resulting from the inability to catabolize GM2 ganglioside by beta-hexosaminidase A (Hex A) due to mutations of the alpha subunit (Tay-Sachs disease) or beta subunit (Sandhoff disease) of Hex A. Hex B (beta beta homodimer) is also defective in Sandhoff disease. We previously developed mouse models of both diseases and showed that Hexa-/- (Tay-Sachs) mice remain asymptomatic to at least 1 year of age while Hexb-/- (Sandhoff) mice succumb to a profound neurodegenerative disease by 4-6 months of age. Here we find that neuron death in Hexb-/- mice is associated with apoptosis occurring throughout the CNS, while Hexa-/- mice were minimally involved at the same age. Studies of autopsy samples of brain and spinal cord from human Tay-Sachs and Sandhoff diseases revealed apoptosis in both instances, in keeping with the severe expression of both diseases. We suggest that neuron death is caused by unscheduled apoptosis, implicating accumulated GM2 ganglioside or a derivative in triggering of the apoptotic cascade.