[Change in refraction and topography after penetrating keratoplasty suture removal]

PURPOSE

To study the refractive and topographic modifications induced by penetrating keratoplasty suture removal.

METHODS

We prospectively studied 80 corneas from 80 patients who had undergone penetrating keratoplasty. All of the eyes were examined before and after all sutures were removed, respectively at 10.9 5.1 months and 21.5 9.6 months after keratoplasty. Subjective refraction, best spectacle-corrected visual acuity (LogMAR units), keratometry, and corneal topography using the EyeSys 2000((R)) device (axial tangential and refractive power) were recorded. Topographies were classified according to the pattern (Bogan classification) and the asphericity shape (prolate and oblate).

RESULTS

Best spectacle-corrected visual acuity (Log MAR units) increased significantly after suture removal (1.1 1.9 lines, plt; 0.001). Suture removal decreased the subjective cylinder (5.01 D 2.06 with suture, 4.11 2.08 without suture; p=0.009). The change in subjective cylinder correlated with the change in topographic pattern(s)=0.67 p<0.001). Conversely to the "bow tie" patterns, the other topographic patterns were more frequent after suture removal. The change in visual acuity was essentially explained by the change in subjective cylinder(s)=0.40 p=0.002). The average central corneal power decreased significantly after suture removal by 0.83 to 1.81 D (p<0.001), whereas the subjective spherical equivalent increased (hyperopization) (-4.07D 3.73 with suture, -3.48 3.40 without suture; p=0.02). The change in central corneal power significantly correlated with the change in subjective spherical equivalent (r(s)()>0.30 plt; 0.001). The corneal power of the mid-periphery did not significantly change after suture removal. Suture removal significantly modified the asphericity shape distribution. (majority of prolate shape with suture, majority of oblate shape without suture, p<0.001).

CONCLUSION

Keratoplasty sutures induce a central bulge in the corneal graft. Suture removal induces a decrease in the subjective cylinder and it increases the subjective spherical equivalent (hyperopization) through a decrease in the central corneal power. Suture removal modifies the corneal topographic pattern and shape. Visual acuity improvement after suture removal is mainly explained by the decrease in subjective astigmatism.

Testing a degradable topical varnish of cetylpyridinium chloride in an experimental dental biofilm model

Dental biofilms are highly associated with the development of dental caries. Novel drug delivery systems are being developed in order to eliminate cariogenic bacteria from the dental biofilms. We formulated two degradable sustained release varnishes, based on acrylic resin, with cetylpyridinium chloride (CPC) as the active agent. These formulations were tested in a dental biofilm model. The retention of CPC in the biofilm was dependent upon the pharmaceutical additives of the varnish. Both varnishes decreased bacterial adhesion, while also demonstrating marked antibacterial properties against the bacteria in the biofilm.

Axonal elongation through long acellular nerve segments depends on recruitment of phagocytic cells from the near-nerve environment. Electrophysiological and morphological studies in the cat

The distal nerve stump plays a central role in the regeneration of peripheral nerve but the relative importance of cellular and humoral factors is not clear. We have studied this question by freezing the tibial nerve distal to a crush lesion in cat. The importance of constituents from the near-nerve environment was assessed by modification of the contact between the tibial nerve and the environment. Silicone cuffs, containing electrodes for electrophysiological assessment of nerve regeneration, were placed around the tibial nerve distal to the crush site. The interaction between long acellular frozen nerve segments (ANS) and the near-nerve environment was ascertained by breaching the silicone cuff to allow access of cellular or humoral components. Tibial nerves were crushed and frozen for 40 mm and enclosed in nerve cuffs with 0.45-microm holes or 2.0-mm holes to allow access of humoral factors or tissue ingrowth, respectively. In a second set of experiments, tibial nerves were crushed and either frozen for 20+20 mm, leaving a 10 mm segment with viable cells in the center (stepping-stone segment) or frozen for 50 mm. These nerves were enclosed in cuffs with 2.0 mm holes corresponding to the viable nerve segment. The regeneration was monitored electrophysiologically by implanted electrodes and after 2 months the nerves were investigated by light and electron microscopy. The results indicate that soluble substances in the near-nerve environment, such as nutrients, oxygen or tropic substances did not exert any independent beneficial effect on the outgrowing axons. However, phagocytic cells entering the acellular segment from the near-nerve environment were crucial for axonal outgrowth in long ANS.

Outcome of Corneal transplantation rejection

PURPOSE

To identify predictive factors for reversibility of corneal graft rejection.

METHODS

The study design was a prospective cohort study. Among 440 consecutive penetrating keratoplasties performed at our institution, 79 grafts from 79 patients who developed signs of transplant rejection were included. Donor, recipient, surgical, and rejection variables were studied, at both univariate and multivariate levels.

RESULTS

The rate of reversibility was 51% (40/79). The average postoperative time of rejection was 10.5 +/- 9.3 months, and the average time of visual acuity recovery in patients with reversible rejection was 2.4 +/- 2.3 months. In logistic regression, only two variables significantly influenced the rate of reversibility. The preoperative diagnosis (p = 0.04) influenced the rate of rejection reversibility; patients with bullous keratopathy or regraft were more likely to experience irreversible rejection than patients with keratoconus or Fuchs' dystrophy. The average graft thickness at the time of rejection diagnosis was 774 +/- 129 microm in patients with irreversible rejection and 681 +/- 118 microm in patients with reversible rejection (p = 0.001).

CONCLUSION

Rejection was reversible in half of the cases. Rejection was more likely to be irreversible in patients with marked increase in graft thickness and in patients transplanted for bullous keratopathy or graft failure. Donor variables did not influence rejection reversibility.

Oxidative damage following cerebral ischemia depends on reperfusion - a biochemical study in rat

The extent of brain injury during reperfusion appears to depend on the experimental pattern of ischemia/reperfusion. The goals of this study were: first, to identify the rate of free radicals generation and the antioxidant activity during ischemia and reperfusion by means of biochemical measurement of lipid peroxidation (LPO) and both enzymatic (superoxide dismutase - SOD, catalase - CAT, glutathione peroxidase - GPx) and non-enzymatic antioxidants activity (glutathione - GSH); and second, to try to find out how the pattern of reperfusion may influence the balance between free radical production and clearance. Wistar male rats were subject of four-vessel occlusion model (Pulsinelly & Brierley) cerebral blood flow being controlled by means of two atraumatic arterial microclamps placed on carotid arteries. The level of free radicals and the antioxidant activity were measured in ischemic rat brain tissue homogenate using spectrophotometrical techniques. All groups subjected to ischemia shown an increase of LPO and a reduction of the activity of enzymatic antioxidative systems (CAT, GPx, SOD) and non-enzymatic systems (GSH). For both groups subjected to ischemia and reperfusion, results shown an important increase of LPO but less significant than the levels found in the group with ischemia only. Statistically relevant differences (p<0.01) between continuous reperfusion and fragmented reperfusion were observed concerning the LPO, CAT, SOD and GSH levels, oxidative aggression during fragmented reperfusion being more important.

Correlation between tear IgE levels and HLA-DR expression by conjunctival cells in allergic and nonallergic chronic conjunctivitis

BACKGROUND

Chronic conjunctival inflammatory diseases may depend upon various mechanisms. Discriminating allergy from nonspecific inflammation has become of striking importance for diagnosis and treatment. We investigated conjunctival inflammatory response by comparing two objective biological tools, tear IgE and HLA-DR expression by conjunctival epithelium, as indirect indicators of activation of the Th2 and Th1 subsets, respectively.

METHODS

Eighty-two patients with chronic conjunctivitis underwent tear IgE measurement by an ELISA technique and quantitation of HLA-DR expression in impression cytology specimens. Forty-two had direct or indirect clinical indications of allergic mechanisms, 26 had chronic conjunctivitis without any sign of allergy, and 14 suffered from isolated nonallergic dry eyes.

RESULTS

Patients clinically considered as allergic only showed positive IgE in 47 of 84 eyes (56%), whereas 21% and 25% of eyes with nonspecific conjunctivitis and dry eyes respectively were also positive. IgE levels were significantly higher in the allergic group than in the other two groups. HLA-DR positivity in epithelial cells was found in 28.5%, 48% and 50% of eyes, respectively. HLA-DR expression by epithelial cells was negatively correlated with tear IgE, as most specimens positive to one criterion were negative to the other one (49 eyes DR+, IgE-; 47 eyes DR-, IgE+; only 9 eyes positive to both criteria; chi-square: P = 0.0001).

CONCLUSION

As IgE synthesis and HLA-DR induction may represent indirect indicators of the activation of the Th2 and Th1 subsets, association of these two simple tests could be interesting for the routine assessment of the mechanisms of inflammatory ocular surface diseases.

[Immediate and late complications of transurethral resection of prostate]

300 patients with benign prostatic hyperplasia admitted in hospital between 1994 and 1998 were studied. The surgical procedure in 21 patients was TUIP (transurethral incision of prostate), in 18 patients was classic adenomectomy (open prostatectomy), in 58 patients classic TURP (transurethral resection of prostate) and in 203 patients TURP by low pressure (hypopressure). The immediate complications in those patients who underwent endoscopic procedures were bleeding in 18 patients, acute urinary infections in 20 patients, endotoxic shock in 5 patients, epididimytis in 9 patients, urine retention in 4 patients, obstruction of catheters in 10 patients, collection of washing liquid in perivesical space (Retzius) in 3 patients. The late complications were the following: bleeding--4 cases, imperative micturition--12 cases, vesicle neck sclerosis--3 cases, urethral orifice stenosis--16 cases, urethral stricture--3 cases, urinary retention--6 cases, abscess in perivesical space (Retzius)--1 case. After TURP in hypopressure, the complications were less frequent due to a better visualization a more rapid execution of the procedure.

Platinum-group elements: quantification in collected exhaust fumes and studies of catalyst surfaces

Automotive catalytic converters, in which Pt, Pd and Rh (platinum-group elements; PGEs) are the active components for eliminating several noxious components from exhaust fumes, have become the main source of environmental urban pollution by PGEs. This work reports on the catalyst morphology through changes in catalyst surface by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and laser-induced breakdown spectrometry (LIBS) from fresh to aged catalytic converters. The distribution of these elements in the fresh catalysts analysed (Pt-Pd-Rh gasoline catalyst) is not uniform and occurs mainly in a longitudinal direction. This heterogeneity seems to be greater for Pt and Pd. PGEs released by the catalysts, fresh and aged 30,000 km, were studied in parallel. Whole raw exhaust fumes from four catalysts of three different types were also examined. Two of these were gasoline catalysts (Pt-Pd Rh and Pd-Rh) and the other two were diesel catalysts (Pt). Samples were collected following the 91,441 EUDC driving cycle for light-duty vehicle testing. The results show that at 0 km the samples collected first have the highest content of particulate PGEs and although the general tendency is for the release to decrease with increasing number of samples taken, exceptions are frequent. At 30,000 km the released PGEs in gasoline and diesel catalysts decreased significantly. For fresh gasoline catalysts the mean of the total amount released was approximately 100, 250 and 50 ng km(-1) for Pt, Pd and Rh, respectively. In diesel catalysts the Pt release varied in the range 400-800 ng km-1. After ageing the catalysts up to 30,000 km, the gasoline catalysts released amounts of Pt between 6 and 8 ng km(-1), Pd between 12 and 16 ng km(-1) and Rh between 3 and 12 ng km(-1). In diesel catalysts the Pt release varied in the range 108-150 ng km(-1). The soluble portion of PGEs in the HNO3 collector solution represented less than 5% of the total amount for fresh catalysts. For 30,000 km the total amount of soluble PGEs released was similar or slightly higher than for 0 km.

Early electrocortical changes consistent with ischemic preconditioning in rat

Ischemic preconditioning (IPC) of the brain describes the neuroprotection induced by a short, conditioning ischemic episode (CIE) to a subsequent severe (test) ischemic episode (TIE). Most of the supporting evidence for IPC is based on histological assessment, several days after TIE. The aim of this study is to investigate if changes induced by IPC can be detected within 30 min of reperfusion following the ischemic episode. A rat model of "four-vessel occlusion" transient global cerebral ischemia and parametric analysis of electrocorticogram were used. A control group was subjected directly to a 10 min TIE, and in a preconditioned group TIE was induced 48 h after a 3 min CIE. Quantitative histology was performed 48 h after TIE. Our key finding is that, 30 min after reperfusion, there is a significant increase in the electrocortical slow activity in the control group but not in the preconditioned group. Moreover the increase inversely correlates with the degree of electrocortical suppression during seconds 10 to 15 after the onset of the ischemic episode.

[Acute closure-angle glaucoma after treatment with ipratropium bromide and salbutamol aerosols]

We report a case of acute angle-closure glaucoma in a patient treated with bronchodilator nebulization. An 82-year-old man with chronic obstructive bronchopathy was treated for acute respiratory decompensation with salbutamol and ipratropium bromide aerosols. Twenty-four hours after beginning the treatment, the patient developed acute angle-closure glaucoma which resolved rapidly with appropriate treatment. The case emphasizes the importance of precautionary measures (waterproof glasses and inhalation masks). In addition patients with a high risk of angle-closure glaucoma should be detected prior to prescribing bronchodilating aerosols.

Cyclooxygenase activity in chondrocytes from osteoarthritic and healthy cartilage

OBJECTIVES

To compare prostaglandin production and cyclooxygenase activity in high-density primary cultures of chondrocytes from patients with osteoarthritis and from healthy controls.

METHODS

Chondrocytes harvested from operative specimens obtained during hip or knee arthroplasty were cultured at a very high density for 48 h. Cyclooxygenase activity was evaluated based on prostaglandin E2 levels (radioimmunological assay) after addition of arachidonic acid. The chondrocytes were cultured with and without IL-1 beta and TNF alpha.

RESULTS

Prostaglandin E2 production and cyclooxygenase activity were significantly higher in cultures of chondrocytes from osteoarthritic than from healthy joints. Adding IL-1 beta to the osteoarthritic chondrocyte cultures further increased the high cyclooxygenase activity, whereas adding TNF alpha alone had no effect.

CONCLUSION

Cultured chondrocytes from osteoarthritic joints showed increased prostaglandin E2 production and cyclooxygenase activity.

[Value of lacrymal IgE determination and conjunctival cytology in the diagnosis of chronic conjunctivitis]

PURPOSE

Chronic conjunctival inflammatory diseases may depend upon various strongly intricated mechanisms. Discriminating allergy from nonspecific inflammation has become of striking importance for diagnosis and treatment. We investigated conjunctival inflammatory response by comparing two objective biological tools, tear IgE detection and HLA DR expression by conjunctival epithelium, as indirect indicators of activation of the Th1 and Th2 subsets, respectively.

METHODS

Sixty-eight patients (135 eyes) with chronic conjunctivitis underwent tear IgE dosage by an ELISA technique and quantification of HLA DR expression in impression cytology specimens. 34 had direct or indirect clinical indications of allergic mechanisms, 22 had chronic conjunctivitis without any sign of allergy, and 12 suffered from isolated nonallergic dry eyes.

RESULTS

Patients clinically considered as allergic only showed positive IgE in 31 out pf 68 eyes (46 per cent), whereas 11/44 (25%) and 7/24 (29%) eyes with nonspecific conjunctivitis and dry eyes respectively were also positive. HLA DR positivity in epithelial cells was found in 18/61 (29.5%), 15/40 (37.5%) and 9/22 (41%) eyes, respectively. HLA DR expression by epithelial cells was negatively correlated with tear IgE, as most specimens positive to one criterion were negative to the other one (37 eyes DR+ IgE-, 35 eyes DR- IgE+, and 5 eyes DR+ IgE+; chi-square: p = 0.0001).

CONCLUSION

As IgE synthesis and HLA DR induction may represent indirect indicators of the activation of the Th1 and Th2 subsets, association of these two simple tests could be interesting for the routine assessment of the mechanisms of inflammatory ocular surface diseases.

The quantification of intrahemispheric EEG asymmetry in rat

We have developed a simple model to quantify the intrahemispheric asymmetries (IA) present in the background EEG activity (BEA), of the adult rat during restrained wakefulness and anesthesia with Ether and chloral hydrate (CHL). We used a collectivity of 40 adult (140 g) male Wistar rats. The epidural EEG activity, was quantified within the 1-30 Hz band by six numerical parameters: root mean square (RMS), mean spectral frequency (MSF), spectral edge frequency at 95% (SEF95) and the relative spectral power (RSP) within the Theta (4.5-7.5 Hz), Alpha (7.5-12 Hz) and Beta (12.5-30 Hz) bands. A significant IA was considerate when simultaneously present in both hemispheres at p (t-Test) < 0.05. The only IA detected in the BEA of the awake restrained rat was the increased theta RSP over the fronto-parietal areas. The theta asymmetry was abolished under both types of anaesthesia. While ether had a global effect on BEA, CHL induced a strong IA reflected in all parameters except RMS and Theta RSP. The fronto-parietal areas seem to be relatively resistant to CHL. It is discussed that the intrahemispheric theta dominance over the frontoparietal areas should be regarded as an indicator of alertness in rats.

Preliminary EEG study of protective effects of Tebonin in transient global cerebral ischemia in rats

Free radicals and platelet activating factor (PAF) have been implicated as important mediators in neuronal injury after cerebral ischemia-reperfusion and, particularly, in postischemic hypoperfusion. The electroencephalography (EEG) is a real time reflection of changes in neuronal activity and metabolism. The objective of this study was to investigate the effects of preventive treatment with Ginkgo biloba extract (EGb 761--Tebonin) in cerebral global ischemia and reperfusion in rats using computerized EEG analysis. Ginkgo biloba extract, known to be, in vitro, a free radicals scavanger and a PAF--antagonist, was administrated in dose of 100 mg/kg over 24 hours, for 5 days before and 5 days after cerebral ischemia--reperfusion. The apparition of isoelectric EEG (flat-line) following 4-vessel occlusion was observed after a mean time of 25 sec. in Ginkgo biloba treated rats and after 18 sec. in control rats (p < 0.0015). Computerized spectral analysis of EEG has shown that the percentage of slow waves at 10 minutes after reperfusion was 117% higher in control group than in Ginkgo biloba group (p < 0.015) and the percentage of slow waves after 15 minutes of reperfusion was 100% higher in the control group than in the Ginkgo biloba group (p < 0.02). Five days after cerebral ischemia--reperfusion the percentage of slow waves was unsignificantly higher in the control group than in the Ginkgo biloba group (p > 0.05).

EEG differences between the opioid and adrenergic psyhoneuroendocrine rat types

Our work is based on the hypothesis of the existence of an opioid psychoneuroendocrine type named "O" type (Cristea, 1993), opposed to the well known adrenergic "A" type described by Roseman and Friedman in 1980. In the present study we tested the differences between the background EEG activity (BEA) of the "O" and "A" rat types during restrained wakefulness and anesthesia with Ether and chloral hydrate (CHL). The differentiation of the psyhoneuroendocrine rat types was made using the level of painful sensitivity. 13 hypersensitive "A" and 14 hyposensitive "O" rats were selected from a 91 adult (140 g) male Wistar population using the distribution of the tail retraction time (TRT) during a tail-flick test. The epidural EEG activity, was quantified within the 1-30 Hz band by six numerical parameters: root mean square (RMS), mean spectral frequency (MSF), spectral edge frequency at 95% (SEF95) and the relative spectral power (RSP) within the Theta (4.5-7.5 Hz), Alpha (7.5-12 Hz) and Beta (12.5-30 Hz) bands. The quantification method used was able to detect statistically significant differences between the two psyhoneuroendocrine rat types during consciousness and light ether anesthesia but failed to show any differences during the deep CHL anesthesia. The particularities were shown to be topographically related with the fronto-parietal regions were "O" type showed a higher SEF95 during the awake restrained state. The pain sensitive "A" type showed a significant intrahemispheric theta RSP asymmetry both during consciousness and ether anesthesia while no such theta gradient could be shown for the "O" type. The differences between the "A" and "O" types are enhanced under light Ether anesthesia to which the "A" type is more resistant. The EEG complementarity between the "A" and "O" types is discussed.

"The cerebral heart"

The aim of this study is to prove that the systolic increase of the intracranial pressure affects the cerebral activity. Since the systolic stress on the cerebral parenchyma reaches its maximal power on the third ventricular wall, it was stated that the nonspecific mechanical stimuli must affect the thalamic nuclei. Simultaneous EEG-ECG recording shows that the alpha activity presents amplitude fluctuations related to the cardiac cycle. The primary thalamic spindles, when present in the EEG recordings, show the rise in amplitude related to the T wave on the ECG. Thus, the rhythmic pulsatile mechanical stress on the thalamic nuclei due to the cardiac cycle acts like a "cerebral heart" on the cortical activity.

Inhibition of plaque formation by local application of a degradable controlled release system containing cetylpyridinium chloride

The effect of a degradable controlled release system containing cetylpyridinium chloride (CPC) on plaque accumulation and gingivitis was evaluated when applied on the anterior teeth of volunteers (16-17 years) over 4 weeks. At baseline, plaque index (PI) and gingival index (GI) of the Ramfjord teeth were measured in the experimental and placebo groups, including 23 and 21 participants respectively. Following scaling and root planning, the participants were instructed to brush, using one brush stroke, the film-forming solution on the buccal surface of the maxillary and mandibular incisors, 1 x a day before bedtime. The applied active solution contained 9 mg of CPC (approximately 80 mg of 11% CPC solution), while the placebo solution was identical in formation, but without the active agent. After 4 weeks, in the CPC-applied group, the recorded PI scores were 0.52 (+/- 0.56) in the anterior area and 1.31 (+/- 0.80) in the posterior area, whereas the corresponding areas in the placebo group reached 1.25 (+/- 0.74) and 1.51 (+/- 1.00), respectively. The PI = 0 frequency in the buccal anterior surfaces after 4 weeks was 54.6% (+/- 38.7%) in the experimental group as compared with 21.9% (+/- 29.0%) in the placebo group (p = 0.005). In contrast to the anterior teeth, there was no significant difference between groups with respect to the PI scores in the non-applied posterior teeth. It may be postulated that the impressive 58% inhibition of plaque accumulation at the site of application is the result of an increase of the substantivity of the CPC due to its incorporation in the film-forming degradable controlled release system.

Ménière's attacks associated with facial paralysis

An 85-year-old man developed in the last 5 years three attacks on Ménière's syndrome associated with facial paralysis. The syndrome could be interpreted as a transient ischemic attack in the territory of the anterior inferior cerebellar artery. An alternative hypothesis could be to admit a Ménière's disease with compression of the facial nerve during the attacks of labyrinthine hydrops.

[Transient global amnesia (a study of 30 cases)]

The authors have studied 30 patients with transient global amnesia aged between 49 and 76 years (median age of 63 years), without focal neurologic signs that have been followed for periods varying between 6 months and 10 years. Three of the patients had recurrent attacks of transient global amnesia, and another three had a stroke, although at some distance from the amnesia attack. Association was noted with certain risk factors including high blood pressure, and angiopathic changes of the eye fundus (in 50% of the patients), dyslipidemia (in 30%), diabetes (in 10%), and essential polyglobulia (in 7%). Coagulation studies including thrombelastograms were carried out in 22 patients, and demonstrated hypercoagulability in 50% of them. Changes in the arterial wall were noted in 85% of the 14 patients in whom carotid sphygmograms were recorded. The presence of these risk factors could explain the occurrence of cerebrovascular accidents in patients with transient global amnesia. Electroencephalograms performed immediately or a short time after the amnesia attack have evidenced in 18 patients rapid-type dysrhythmia, or diffuse theta waves, predominantly located in the deep layers of the left and right temporal areas. The EEG tracings were either flat or normal in the remaining 12 patients. Of the 30 patients presenting with global transient amnesia only two had migraine in antecedents, and another six had headache during the evolution of amnesia. The neurologic examination did not reveal any abnormality in 27 of the patients. Sequelar signs of neurological deficits were noted in the remaining three patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal variations in the muscarinic regulation of acetylcholine release from Torpedo electric organ nerve terminals

The cholinergic nerve endings of the electric organs of Torpedo ocellata contains presynaptic muscarinic acetylcholine receptors (mAChR) which regulate acetylcholine (ACh) release by negative feedback. The efficiency of this muscarinic regulation varies circannually: maximal inhibition is observed in the winter, much smaller effects in the fall and spring, and no effect is observed during the summer. These variations are accompanied by seasonal changes in the ability of the mAChR to trigger the synthesis of its second messenger (a prostaglandin E-like substance) and in the ability of exogenous prostaglandin E2 to inhibit ACh release. No seasonal changes were found in the number of presynaptic mAChRs. These findings suggest that the observed seasonal variations are due to changes in both the metabolism of prostaglandins in the electric organ and the sensitivity of the ACh-releasing apparatus to the muscarinic second messenger.