Low-frequency depression of synaptic responses recorded from rat visual cortex

To characterize the low-frequency depression (LFD) of synaptic transmission in the visual cortex, we recorded field potentials and minimal excitatory postsynaptic potentials (EPSPs) from layer II/III following intracortical stimulation at various frequencies in cortical slices of rats. Field potentials were stable at 0.017 Hz, but showed an amplitude depression at 0.033-0.1 Hz at stimulus intensity of 1.5 times the threshold for induction of the postsynaptic component and at 0.1-0.2 Hz at intensity of 1.2 times the threshold. The LFD was input-specific and its magnitude correlated with the stimulus frequency. An interruption of stimulation for 15 min yielded a nearly complete recovery from LFD. Minimal EPSPs tested at 0.1-1.7 Hz often showed LFD with similar features. However, some inputs were stable or even facilitated during repeated stimulation. At 0.1 and 0.2 Hz, >50% of inputs were stable, whereas 10% and 25% were depressed, respectively. At 0.5 and 1.7 Hz, LFD was observed in >60% and 80% of inputs, respectively. The magnitude of LFD strongly varied across inputs. In 3 of the 41 inputs analyzed, LFD was so strong that these inputs became virtually silent. Occurrence of responses to the second pulse in the paired-pulse paradigm when the first response was absent and recovery of depressed EPSPs following stimulus interruption or shift to a lower frequency suggest that these synapses were presynaptically silent due to a lowered probability of transmitter release. Altogether, the results indicate that testing intervals of <10 or even < or =30 s cannot be regarded as completely neutral. At the single-cell level, frequency-dependent changes were strongly heterogeneous across different inputs. LFD and its spontaneous recovery may underlie the previously described "post-rest" potentiation, and should be taken into account when considering information processing in cortical networks.

Inactivation differences of microorganisms by low pressure UV and pulsed xenon lamps

UV disinfection has been applied to water treatment in recent years with low-pressure and medium-pressure UV lamps mainly used as the light source. In general, UV disinfection is considered to be inefficient with water of high turbidity because of inhibition of light penetration. Additionally, photoreactivation may be a problem that should be considered in case a disinfected water is discharged to the environment where sunlight causes reactivation. Recently, other types of lamps have been proposed including a flush-type lamp (such as a pulsed-xenon lamp) that emits high energy and wide wavelength intermittently. In this study, the difference between inactivation efficiencies by low-pressure UV (LPUV) and pulsed-xenon (PXe) lamps was investigated using two coliphage types and three strains of Escherichia coli. PXe had a suppressive effect on photoreactivation rate of the E. coli strains even though there was no significant effect on inactivation rate and maximum survival ratio after photoreactivation. PXe also had a benefit when applied to high turbidity waters as no tailing phenomena were observed in the low survival ratio area although it was observed in LPUV inactivation. This efficiency difference was considered to be due to the difference in irradiated wavelength of both lamps.

Subclinical renal tubular acidosis in patients with primary and secondary Sjögren's syndrome: a possible marker of disease progression

Abstract To clarify the prevalence of subclinical renal tubular acidosis (RTA) and its association with clinical and laboratory parameters in primary and secondary Sjögren's syndrome (SS), an acid-loading test was conducted. Subclinical RTA was found in 32% of patients with SS. The prevalence of subclinical RTA in primary and secondary SS was about the same (31.6% and 33.3%, respectively). Significant longer duration of illness, more severely decreased salivary excretion, decreased lymphocyte number, higher serum levels of IgG and IgA, and higher frequency of anti-SS-A (Ro) and SS-B (La) antibodies were found in patients with subclinical RTA. These results suggested that subclinical RTA may be a characteristic manifestation both in primary and secondary SS, along with the progression of immunologic dysfunction, when the illness seemed to be indolent.

Immunosuppressive properties of human amniotic membrane for mixed lymphocyte reaction

The combination of allograft limbal transplantation (ALT) and amniotic membrane transplantation (AMT) has been applied in the treatment of severe ocular surface diseases. The beneficial effect of this combination has been thought to result from possible immunosuppressive ability of amniotic membrane (AM). However, the mechanisms of any such ability remain unknown. In this study, we investigated whether human AM has the ability to suppress allo-reactive T cell responses in vitro. For mixed lymphocyte reaction (MLR), lymphocytes isolated from lymph nodes of C57BL/6 mice (Mls1b, Vbeta6+) were cultured with irradiated splenocytes from DBA/2 mice (Mls1a, Vbeta6-) with or without human AM. For carboxyfluorescein diacetate succinimidyl ester (CFSE) experiments, responder lymph node cells were labelled with a stable intracellular fluorescent dye and cultured with irradiated stimulator cells. The ratio of responder Vbeta6+ T cells was then determined by FACS analysis, and the division profiles of responder Vbeta6+ T cells were analysed by CFSE content. Furthermore, Th1 and Th2 cytokine synthesis by allo-reactive T cells in MLR culture supernatants was determined by enzyme-linked immunosorbent assay (ELISA). Addition of AM to the MLR culture resulted in the significant inhibition of thymidine incorporation compared with control culture lacking AM. The population of responder CD4+Vbeta6+ T cells was significantly reduced in the AM-treated culture in comparison to control. CFSE analysis revealed less division and lower proliferation of responder CD4+Vbeta6+ T cells in cultures with AM than without. In addition, allo-rective T cell synthesis of both Th1 (IL-2 and IFNgamma) and Th2 (IL-6 and IL-10) type cytokine was significantly decreased in the presence of AM. These results indicate that human AM has the ability to suppress allo-reactive T cells in vitro. This inhibitory effect likely contributes to the success of the ALT-AMT combination.

Plasma of patients with Upshaw-Schulman syndrome, a congenital deficiency of von Willebrand factor-cleaving protease activity, enhances the aggregation of normal platelets under high shear stress

Upshaw-Schulman syndrome (USS) is an autosomal recessive disorder characterized by repeated episodes of chronic thrombocytopenia and microangiopathic haemolytic anaemia (MAHA) that responds dramatically to infusions of fresh frozen plasma (FFP). Recent studies have provided consistent evidence that USS is a congenital deficiency of plasma von Willebrand factor-cleaving protease (VWF-CPase) activity and, therefore, unusually large VWF multimers (UL-VWFMs) are present in the plasma. However, the molecular mechanism of the clinical symptoms of USS is not well understood. We studied the relationship between UL-VWFMs and thrombocytopenia in two USS patients by analysing platelet aggregation using a mixture of the patient's plasma and normal washed platelets under high shear stress. Our results clearly showed a remarkably enhanced high shear stress-induced platelet aggregation (H-SIPA) by the patient's plasma. At 24 h after FFP infusion (approximately equal to 10 ml/kg body weight), the enhanced H-SIPA became almost completely normalized but, 2 d later, it began to return to the preinfusion level. These results were in accordance with the change in VWFM patterns. The specific effects of enhanced H-SIPA on VWF, platelet glycoprotein Ib and endogenous ADP released from platelets upon stimulation were confirmed using reagents that specifically inhibit their respective functions. Our present results clearly indicate that thrombocytopenia in USS patients is caused by a combination of the presence of UL-VWFMs, platelets and high shear stress generated in the microcirculation.

Vitreous hemorrhage from a ciliary granuloma associated with Wegener granulomatosis

PURPOSE

To report a case of vitreous hemorrhage from ciliary granuloma in Wegener granulomatosis.

METHODS

Interventional case report. An 18-year-old woman with Wegener granulomatosis and episcleral granuloma in her LE had ultrasound biomicroscopy findings of a mass in the pars plana of the ciliary body in the meridian corresponding to the episcleral granuloma.

RESULTS

The patient underwent vitrectomy in the LE for subsequent vitreous hemorrhage. Intraoperatively, the mass was diagnosed as a ciliary granuloma at the pars plana. Dense blood clotting around the ciliary granuloma and subretinal exudation at the ora serrata were observed, with no other changes causative for the vitreous hemorrhage.

CONCLUSIONS

We report a case of vitreous hemorrhage associated with a ciliary granuloma that was revealed by ultrasound biomicroscopy. Careful observation is necessary in eyes with persistent inflammation in Wegener granulomatosis.

[A case of postoperative gastric cancer responding to adjuvant chemotherapy with TS-1--a novel oral formation of 5-fluorouracil]

TS-1 is a novel oral formation of 5-fluorouracil, developed using tegafur and two biochemical modulations. We report the case of a patient with multiple lymph node metastases from gastric cancer that markedly responded to TS-1. A 70-year-old man suffering from hematemesis was admitted to our hospital. Computed tomography showed advanced gastric cancer with huge lymph node metastases. After non-curative operation, he received adjuvant chemotherapy with TS-1 for 12 weeks. CT revealed that almost complete reduction of the metastatic nodes was obtained. No serious adverse reactions were observed.

Vitreous levels of insulin-like growth factor-I in patients with proliferative diabetic retinopathy

The levels of IGF-I in the vitreous body and the intraocular fluid of patients with proliferative diabetic retinopathy (PDR) were determined using radioimmunoassay (RIA). Eleven vitreous specimens were obtained from the intraocular fluid of eyes of patients with PDR who underwent surgery during the operation. Eleven intraocular fluids from the same patients during reoperations were compared with controls. The expression of IGF-I mRNA in cultured human Muller glial cells was evaluated using reverse transcription-polymerase chain reaction (RT-PCR). The mean IGF-I level in the vitreous samples during initial PDR surgery and reoperation was significantly higher than that found in the vitreous of the control (p < 0.05). The level of IGF-I increased in 6 of the 11 cases. Cultured human Muller cells expressed IGF-I mRNA. The results indicate increased levels of IGF-I both in the initial vitreous and ocular fluid at post-operative re-proliferation. Muller cell is suggested as an origin of local IGF-I production.

Self-assisted tandem Michael-aldol reactions of alpha,beta-unsaturated ketones with aldehydes

The tandem Michael-aldol reaction of 1-[2-(methylsulfanyl)-phenyl]prop-2-en-1-one (1) or the seleno congener 4 with p-nitrobenzaldehyde in the presence of BF3.Et2O gave the Baylis-Hillman adduct 2 or 5 and onium salt 3 or 6, respectively, and selenochromanone 7 from 4.

Cultivated corneal epithelial stem cell transplantation in ocular surface disorders

PURPOSE

To investigate the outcome of cultivated corneal epithelial transplantation for severe stem cell deficiencies using denuded amniotic membrane (AM) as a carrier.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Thirteen eyes of 11 patients were studied. These consisted of five eyes with acute Stevens-Johnson syndrome (SJS), two with chronic SJS, one with an acute chemical injury, two with chronic chemical injuries, two with ocular cicatricial pemphigoid, and one with drug-induced pseudopemphigoid. All of these eyes had total stem cell deficiencies.

MAIN OUTCOME MEASURES

Adaptation of the cultivated corneal epithelium onto the host corneal surface was confirmed 48 hours after surgery. The reconstruction of the ocular surface and visual acuity were measured.

METHODS

Corneal limbal epithelium from donor corneas was cultivated for 4 weeks on a denuded AM carrier, with 3T3 fibroblast coculture and air lifting. The cultivated corneal epithelium showed four to five layers of stratification and was well differentiated. After conjunctival tissue removal from the cornea up to 3 mm outside the limbus and subconjunctival tissue treatment with 0.04% mitomycin C, cultivated allocorneal epithelium, including the AM carrier, was transplanted onto the corneal surface up to the limbus. Lamellar keratoplasty, using preserved donor graft without epithelium, was performed simultaneously for five chronic-phase patients showing corneal stromal scarring. Systemic immunosuppression was used to prevent allograft rejection.

RESULTS

In all 13 eyes, the entire corneal surface, on which cultivated allocorneal epithelium had been placed, was free from epithelial defects 48 hours after surgery, indicating complete survival of the transplanted corneal epithelium. Visual acuity improved in all eyes after surgery, and 10 of the 13 eyes were restored to good vision (postoperative visual acuity improved two or more lines) 6 months after the operation. During the follow-up period (mean +/- standard deviation, 11.2 +/- 1.3 months), the corneal surfaces were clear, although three eyes experienced epithelial rejection.

CONCLUSIONS

Cultivated corneal epithelial transplantation using denuded AM as a carrier can be used for severe stem cell deficiencies.

Characteristics of the human ocular surface epithelium

An appreciation of the biological characteristics of the human ocular surface epithelium affords us a great insight into the physiology of the human ocular surface in health and disease. Here, we review five important aspects of the human ocular surface epithelium. First, we recognize the discovery of corneal epithelial stem cells, and note how the palisades of Vogt have been suggested as a clinical marker of their presence. Second, we introduce the concept of the gene expression profile of the ocular surface epithelium as arrived at using a new strategy for the systematic analysis of active genes. We also provide a summary of several genes abundantly or uniquely expressed in the human corneal epithelium, namely clusterin, keratin 3, keratin 12, aldehyde dehydrogenase 3 (ALDH3), troponin-I fast-twitch isoform, ssig-h3, cathepsin L2 (cathepsin V), uroplakin Ib, and Ca(2+)-activated chloride channel. Genes related to limbal and conjunctival epithelia are also described. Third, we touch upon the genetic abnormalities thought to be involved with epithelial dysfunction in Meesmann's dystrophy, gelatinous drop-like corneal dystrophy, and the ssig-h3-mutated corneal dystrophies. Fourth, we provide an update regarding the current state of knowledge of the role of cytokines, growth factors and apoptosis in relation to ocular surface homeostasis and tissue reconstruction; the main factors being epidermal growth factor (EGF), keratinocyte growth factor (KGF), hepatocyte growth factor (HGF), transforming growth factor-ss (TGF-ss), and some inflammatory cytokines. Fifth, corneal epithelial barrier function and dysfunction as measured by fluorophotometry is remarked upon, with an explanation of the FL-500 fluorophotometer and its ability to detect corneal epithelial dysfunction at a subclinical level. The research described in this review has undoubtedly generated a complete understanding of corneal epithelial pathophysiology-an understanding that, directly or indirectly, has helped advance the development of new therapeutic modalities for ocular surface reconstruction.

A novel heat stress-responsive gene in the marine diatom Chaetoceros compressum encoding two types of transcripts, a trypsin-like protease and its related protein, by alternative RNA splicing

We investigated the change of mRNA expression patterns in the laboratory-grown diatom Chaetoceros compressum under heat-stress conditions by mRNA arbitrarily primed (RAP) RT-PCR. Cells grown at 20 degrees C were subjected to heat treatment at 30 degrees C for 15 min and subsequently maintained at 20 degrees C for 8 h. Four genes including HI-5 were detected as heat stress-responsive genes by fingerprint analysis of RAP RT-PCR. Cloning for full-length cDNA sequences of HI-5 transcripts and related genomic DNA analysis revealed that two types of mRNA, HI-5a and HI-5b, were transcribed from the single HI-5 gene. While the HI-5a protein contained a catalytic domain characteristic to trypsin-like proteases, the HI-5b protein lacked this domain due to an insertion in the associated mRNA of 112 nucleotides; this insertion sequence contained a stop codon near the central region. Quantitative RT-PCR was performed to investigate the changes in expression levels of the two types of mRNA following heat treatment. The HI-5b transcripts were constitutively expressed in both unstressed and heat-stressed cells. In contrast, the number of HI-5a transcripts markedly increased in cells immediately after heat stress, reaching levels 19-fold higher at 8 h after heat stress than that in unstressed cells. These results suggest that RNA splicing plays a key role in heat stress-dependent expression of the HI-5a and HI-5b transcripts from the single HI-5 gene in the diatom.

Paraoxonase gene polymorphisms and plasma oxidized low-density lipoprotein level as possible risk factors for exudative age-related macular degeneration

PURPOSE

Paraoxonase (E.C.3.1.1.2) is a polymorphic protein shown to prevent low-density lipoprotein oxidation. Our purpose is to evaluate the hypothesis that paraoxonase gene polymorphisms and plasma oxidized low-density lipoprotein level play a role in the occurrence of exudative age-related macular degeneration.

METHODS

We analyzed paraoxonase genotypes (A/B, Gln-Arg192 and L/M, Leu-Met54) and plasma oxidized low-density lipoprotein levels in 72 unrelated Japanese patients with exudative age-related macular degeneration and compared the results with those of 140 age-matched and sex-matched control subjects.

RESULTS

The distribution of paraoxonase 192 and paraoxonase 54 polymorphisms was significantly different between the patients with age-related macular degeneration and control subjects (chi-square = 6.226, P =.0445, and chi-square = 6.863, P =.0323, respectively). The high frequency of the BB genotype at position 192 was observed in the exudative age-related macular degeneration group compared with control subjects (52.8% vs 35.0%, respectively; P =.0127). The high frequency of the LL genotype at position 54 was observed in the patients more than the controls (91.7% vs 77.1%, respectively; P =.0090). The mean (+/- SE) oxidized low-density lipoprotein levels in the patients was significantly higher than in the controls (19.1 +/- 1.0 vs 16.2 +/- 0.6 U/ml, P <.01).

CONCLUSION

These results indicate that the paraoxonase gene polymorphisms may represent a possible genetic risk factor for age-related macular degeneration and that increased plasma oxidized low-density lipoprotein may be involved in the pathogenesis of age-related macular degeneration.

Sialic acid in normal human tear fluid

PURPOSE

We measured the concentration of sialic acid, the terminal component of mucin, in normal diluted human tears.

METHODS

Twenty-microliter tear samples were collected from 31 healthy volunteers (average age = 50.7 years) using micropipette after 50 microL instillation of saline. We investigated the correlation of concentration between glycoprotein and sialic acid and the difference between the right and the left eyes, as well as the reproducibility of the sampling procedure.

RESULTS

There was significant correlation of the concentration between glycoprotein and sialic acid (right eye: r = 0.952, P <.0001; left eye: r = 0.976, P <.001). There was no significant difference in concentration between the right and the left eyes. Also, the reproducibility was considered acceptable in three measurements of sialic acid using the present procedure. The sialic acid concentration in normal diluted tears was 37.1 microg/mL on average.

CONCLUSION

Our data indicates that sialic acid concentration is an indicator for the concentration of glycoprotein and that this method of measurement is applicable to the analysis of mucin-deficient disorders.

Upshaw-Schulman syndrome revisited: a concept of congenital thrombotic thrombocytopenic purpura

Upshaw-Schulman syndrome (USS) is a congenital bleeding disorder characterized by repeated episodes of thrombocytopenia and microangiopathic hemolytic anemia that respond to infusions of fresh frozen plasma. Inheritance of USS has been thought to be autosomal recessive, because 2 siblings in the same family are often affected but their parents are asymptomatic. Recently, chronic relapsing thrombotic thrombocytopenic purpura (CR-TTP), reported almost exclusively in adults, was shown to be caused by inherited or acquired deficiency in the activity of a plasma von Willebrand factor-cleaving protease (vWF-CPase). The pathogenesis of USS is unknown, and a relationship between CR-YEP and USS has not been reported. We studied 3 unrelated USS patients (ST, SY, and KI) who presented with severe indirect neonatal hyperbilirubinemia. All 3 patients had undetectable vWF-CPase activity, and the inhibitors to vWF-CPase were all negative. In their parents with no clinical symptoms, vWF-CPase activities as a percentage of control samples (mother/father) were 17/20 for ST, 60/45 for SY, and 36/5.6 for KI. Thus, USS and vWF-CPase activity appear to be coinherited as autosomal recessive traits. Transfusion of fresh frozen plasma in 2 patients (ST and SY) resulted in the expected maximal increment of approximately 7% to 8% in vWF-CPase activity at 1 to 4 hours, but the levels became less than 3% within 2 days. After this decrease, platelet counts increased, plateaued in the normal range at 10 to 12 days, and declined thereafter. Thus, the 2 to 3 weeks of therapeutic benefit from plasma infusions will be discussed in relation to the intravascular lifetime of vWF-CPase.

Ventricular parasystolic couplets originating in the pathway between the ventricle and the parasystolic pacemaker: mechanism of "irregular" parasystole

This article explains the mechanism of "irregular" parasystole. Two theories have been suggested: "electrotonic modulation" and "type I second degree entrance block." This study attempts to clarify the mechanism of irregular parasystole in cases of true ventricular parasystole associated with ventricular parasystolic couplets. Cases associated with ventricular parasystolic couplets were selected from 37 clinical cases of true ventricular parasystole in which one or more pure parasystolic cycles with no intervening nonectopic QRS complexes were found. Of the 37 cases of true ventricular parasystole, ventricular parasystolic couplets were found in 4 cases. In none of the other 33 cases, ventricular parasystolic couplets were found. In all the cases coexisting with ventricular parasystolic couplets, the latter ectopic QRS complex of the couplet failed to reset the parasystolic rhythm. The above findings suggest that the latter ectopic QRS complex of the parasystolic couplet originated not in the parasystolic pacemaker but in the pathway between the ventricle and the parasystolic pacemaker. It seems that when a sinus impulse fell late in the parasystolic cycle, it passed through the site of second degree entrance block and that the parasystolic couplets originated from the reentrant pathway between the ventricle and the pacemaker. This strengthens our previous suggestion that the mechanism of irregular parasystole is governed by "type I second degree entrance block" and not by "electrotonic modulation."

Hospital outbreak of MEN-1-derived extended spectrum beta-lactamase-producing Klebsiella pneumoniae

An outbreak of Klebsiella pneumoniae resistant to broad spectrum cephalosporins occurred in a hospital in the Kinki area in Japan. During 18 months, from February 1998 to July 1999, 23 strains were isolated from 21 patients (10 with pneumonia, 4 with urinary tract infection, 1 with sepsis, 1 with vaginosis, 1 with a wound infection, and 1 with both pneumonia and sepsis; 3 patients showed noninfective colonization with K. pneumoniae) in seven wards, including the intensive care unit. MEN-1-derived gene was detected by polymerase chain reaction from the majority of the strains. Ninety-nine strains of K. pneumoniae were isolated during this period. The isolation rate of K. pneumoniae resistant to broad spectrum cephalosporins was 21%. We distinguished three clones by pulsed-field gel electrophoresis and randomly amplified polymorphic DNA analysis, and one of them was isolated from 18 patients. The presence of an R-plasmid of more than 160 kb was confirmed by plasmid analysis, but it was not possible to obtain transconjugants from all strains. This outbreak of K. pneumoniae was immediately confirmed by genetic analysis, and it was promptly ended by the infection control procedures. This is the first hospital outbreak of MEN-1-producing K. pneumoniae in Japan.

Failure in the Detection of Aberrant mRNA from the Heterozygotic Splice Site Mutant Allele for Protein S in a Patient with Protein S Deficiency

A 29-year-old male patient with acute arterial obstruction and a medical history including thrombosis in the deep veins and pulmonary infarction presented with a reduced level of both protein S (PS) activity and free PS. Sequencing of the genomic PS gene in this patient revealed that the patient was heterozygous for the mutant PS allele, in which a nucleotide substitution occurred at the donor splice site in intron 12 (GT to GA). The patient was heterozygous for PS genes having dimorphic codons for Pro626 (CCA/CCG) and the aberrant allele in this patient was associated with the CCA form. Allelic exclusion of PS expression was demonstrated by use of Pro626 (CCA/CCG) dimorphism and only a normal mRNA sequence derived from the CCG-allele was identified in the patient. These findings suggested that the mutation at the splice site in the PS gene caused either defective production of mRNA or the gene may have produced extremely unstable RNA products, leading to reduced levels of PS activity and free PS in this patient.

[Effect of latanoprost on the barrier function of corneal epithelium]

PURPOSE

We evaluated the effect on corneal epithelium barrier function of instillation of prostaglandin F2 alpha ophthalmic solution (latanoprost) for one month.

MATERIALS AND METHODS

Ten healthy volunteers and nine glaucoma patients were enrolled in this study. The barrier function was determined as uptake of topically applied sodium fluorescein by the central cornea measured with an anterior fluorophotometer(FL-500, Kowa Co. Ltd). Healthy volunteers and glaucoma patients received 0.005% latanoprost instillation once daily for one month. We measured the uptake of fluorescein by the cornea of each subject before and one month after instillation.

RESULTS

Fluorescein uptake before the instillation was 22.2 +/- 16.0 ng/ml (mean +/- standard deviation) and 26.4 +/- 15.1 ng/ml one month after the treatment in the normal group, and it was 55.0 +/- 25.0 ng/ml before treatment and 57.8 +/- 37.0 ng/ml after treatment in the glaucoma group. There was no significant difference in the uptake of fluorescein before and after treatment in either of two groups.

CONCLUSION

These results suggested that the barrier function of corneal epithelium was not compromised after the instillation of latanoprost for at least one month.

The detection of bacteria and bacterial biofilms in punctal plug holes

PURPOSE

An investigation into bacterial biofilm formation on and in punctal plugs.

METHODS

The study involved 21 patients with severe dry eye whose puncta were occluded by the use of punctal plugs. Of these, 15 had Sjögren's syndrome, 3 had non-Sjögren's syndrome, 2 had Stevens-Johnson syndrome, and 1 had graft-versus-host disease. From 17 of the 21 subjects, 18 samples of material were extracted from the holes of the punctal plugs (16 unilateral and 1 bilateral) and were subjected to enrichment culture. Nineteen punctal plugs were removed and processed for electron microscopy: 15 by scanning electron microscopy, and 4 by transmission electron microscopy.

RESULTS

Positive cultures were found in 8 of 18 (44%) samples of the material extracted from the holes of punctal plugs. In six of these eight cases (75%) the cultured bacterial species was Staphylococcus epidermidis, whereas in the other two cases (25%) it was S. aureus. In 8 of the 15 punctal plugs examined by scanning electron microscopy and in the material extracted from 1 plug that was examined by transmission electron microscopy, there was clear evidence of bacterial colonization.

CONCLUSION

Careful observation of patients with punctal plugs is important. If material accumulates in or on a punctal plug, it may contain bacteria and may form a bacterial biofilm. In these cases, replacement of the plug, clearing of the hole, or an alternative treatment should be considered.