Altered cytokine balance in the tear fluid and conjunctiva of patients with Sjögren's syndrome keratoconjunctivitis sicca

PURPOSE

To compare epidermal growth factor (EGF) concentration in tear fluid and levels of inflammatory cytokines in the conjunctival epithelium of patients with Sjögren's syndrome keratoconjunctivitis sicca with those of normal controls.

METHODS

Schirmer 1 tear testing, corneal fluorescein staining and conjunctival impression cytology for quantitation of goblet cell density were performed in ten patients with Sjögren's syndrome-associated keratoconjunctivitis sicca and ten asymptomatic normal controls. ELISA was used to detect the concentration of EGF in tear fluid and interleukin 6 in lysates of conjunctival cytology specimens obtained from all subjects. The levels of RNA transcripts encoding inflammatory cytokines [interleukin 1alpha_(IL-1alpha), interleukin 6 (IL-6), interleukin 8 (IL-8), tumor necrosis factor alpha_(TNF-alpha), and transforming growth factor beta1 (TGF-beta1)] as well as a housekeeping gene (G3PDH) were evaluated in conjunctival cytology specimens taken from all subjects by semiquantitative competitive reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Decreased tear fluid EGF concentration was noted in Sjögren's syndrome patients (mean 0.68 +/- 0.59 ng/ml) compared to controls (mean 1.66 +/- 0.45 ng/ml, P = 0.004). Significantly increased levels of IL-1alpha, IL-6, IL-8, TNF-alpha and TGF-beta1 RNA transcripts were found in the conjunctival epithelium of Sjögren's syndrome patients compared to controls (P < 0.05), while the level of G3PDH was similar in both groups. The concentration of IL-6 protein was significantly higher in Sjögren's syndrome conjunctiva samples (P = 0.012). Tear EGF concentration correlated with Schirmer 1 scores (rho 0.767, P < 0.001), corneal fluorescein staining scores (rho -0.562, P = 0.01), conjunctival goblet cell density (rho 0.661, P = 0.001) and the levels of IL-1alpha_and IL-8 RNA in the conjunctival epithelium (rho -0.677 and -0.747, respectively, P = 0.001). Both IL-1alpha_and IL-8 RNA in the conjunctival epithelium increased as Schirmer 1 scores decreased (P </= 0.001). IL-8 RNA level correlated with corneal fluorescein staining (rho 0.690, P = 0.001) and conjunctival goblet cell density (rho -0.767, P < 0.001). A significant decrease in IL-8 RNA level, corresponding to improvement in irritation symptoms and ocular surface disease, was observed in six eyes after two weeks of topical corticosteroid therapy.

CONCLUSIONS

The balance of cytokines in the tear fluid and conjunctival epithelium is altered in Sjögren's syndrome. The severity of keratoconjunctivitis sicca in this condition increases as tear fluid EGF concentration decreases and levels of inflammatory cytokines in the conjunctival epithelium increase. These findings provide new insight into the pathogenesis of keratoconjunctivitis and provide potential targets for therapy.

Incidence of asymptomatic deep vein thrombosis in patients with COVID-19 pneumonia and elevated D-dimer levels

AIM

An increased risk of venous thromboembolism (VTE) in patients with COVID-19 pneumonia admitted to intensive care unit (ICU) has been reported. Whether COVID-19 increases the risk of VTE in non-ICU wards remains unknown. We aimed to evaluate the burden of asymptomatic deep vein thrombosis (DVT) in COVID-19 patients with elevated D-dimer levels.

METHOD

In this prospective study consecutive patients hospitalized in non-intensive care units with diagnosis of COVID-19 pneumonia and D-dimer > 1000 ng/ml were screened for asymptomatic DVT with complete compression doppler ultrasound (CCUS). The study was approved by the Institutional Ethics Committee.

RESULTS

The study comprised 156 patients (65.4% male). All but three patients received standard doses of thromboprophylaxis. Median days of hospitalization until CCUS was 9 (IQR 5-17). CCUS was positive for DVT in 23 patients (14.7%), of whom only one was proximal DVT. Seven patients (4.5%) had bilateral distal DVT. Patients with DVT had higher median D-dimer levels: 4527 (IQR 1925-9144) ng/ml vs 2050 (IQR 1428-3235) ng/ml; p < 0.001. D-dimer levels > 1570 ng/ml were associated with asymptomatic DVT (OR 9.1; CI 95% 1.1-70.1). D-dimer showed an acceptable discriminative capacity (area under the ROC curve 0.72, 95% CI 0.61-0.84).

CONCLUSION

In patients admitted with COVID-19 pneumonia and elevated D-dimer levels, the incidence of asymptomatic DVT is similar to that described in other series. Higher cut-off levels for D-dimer might be necessary for the diagnosis of DVT in COVID-19 patients.

Suppression of interleukin 1alpha and interleukin 1beta in human limbal epithelial cells cultured on the amniotic membrane stromal matrix

AIMS

Amniotic membrane (AM) transplantation reduces inflammation in a variety of ocular surface disorders. The aim of this study was to determine if AM stroma suppresses the expression of the IL-1 gene family in cultured human corneal limbal epithelial cells.

METHODS

Human corneal limbal epithelial cells were cultured from limbocorneal explants of donor eyes on plastic or on the AM stroma. Transcript expression of IL-1alpha, IL-1beta, IL-1 receptor antagonist (RA), and GAPDH was compared with or without addition of lipopolysaccharide to their serum-free media for 24 hours using RNAse protection assay (RPA). Their protein production in the supernatant was analysed by ELISA.

RESULTS

Expression of IL-1alpha and IL-1beta transcripts and proteins was significantly reduced by cells cultured on the AM stromal matrix compared with plastic cultures whether lipopolysaccharide was added or not. Moreover, expression of IL-1 RA by cells cultured in the lipopolysaccharide-free medium was upregulated by AM stromal matrix. The ratio between IL-1 RA and IL-1alpha protein levels in AM cultures was higher than in plastic cultures.

CONCLUSIONS

AM stromal matrix markedly suppresses lipopolysaccharide induced upregulation of both IL-1alpha and IL-1beta. These data may explain in part the effect of AM transplantation in reducing ocular surface inflammation, underscoring the unique feature of the AM as a substrate for tissue engineering.

Regulation of MMP-9 production by human corneal epithelial cells

The matrix metalloproteinases, MMP-2 and MMP-9, are known to be critical extracellular-remodeling enzymes in wound healing and other diseases of the ocular surface. This study investigated the regulation of MMP-2 and MMP-9 in human corneal epithelial cells by growth factors and pro-inflammatory cytokines (IL-1beta and TNF-alpha) they are exposed to, and by doxycycline, a medication used to treat ocular surface disease. Primary human corneal epithelial cell cultures were treated with one of the following cytokines (IL-1alpha, IL-1beta, IL-6, IL-8, TNF-alpha) or growth factors (EGF, HGF, KGF, PDGF-BB, TGF-alpha, TGF-beta), with or without their corresponding inhibitors. The conditioned media were collected after 24 hr for gelatin zymography and MMP-9 activity assay. Total RNA was extracted from the cells treated for 6 hr and was subjected to RT-PCR and Northern hybridization. Between the two gelatinases, MMP-2 and MMP-9, detected by zymography, the 92 kDa MMP-9 in the conditioned medium was markedly up-regulated by the pro-inflammatory cytokines, IL-1beta and TNF-alpha. The MMP-9 protein and activity were dose-dependently stimulated by IL-1beta or TNF-alpha at 0.1, 1.0 and 10 ng ml(-1). This up-regulation was nearly abolished by neutralizing antibodies (IL-1beta and TNF-alpha) and by IL-1 receptor antagonist. Semi-quantitative RT-PCR and Northern hybridization disclosed that the MMP-9 transcript was also markedly up-regulated in a dose-dependent manner by IL-1beta and TNF-alpha. Doxycycline (10 microg ml(-1)) suppressed MMP-9 protein level and activity, but not its mRNA, that was stimulated by IL-1beta and TNF-alpha (1 ng ml(-1)). In contrast, the 72 kDa MMP-2 was not significantly modulated by any of these cytokines. In conclusion, production of MMP-9 is stimulated by the pro-inflammatory cytokines, IL-1beta and TNF-alpha. These factors may play a role in the pathogenesis of MMP-9 mediated corneal matrix degradation. The efficacy of doxycycline in treating ocular surface diseases may be related to its ability to suppress MMP-9 production in the corneal epithelium.

Update of Guidelines for laparoscopic treatment of ventral and incisional abdominal wall hernias (International Endohernia Society (IEHS))-Part A

Abstract

In 2014, the International Endohernia Society (IEHS) published the first international “Guidelines for laparoscopic treatment of ventral and incisional abdominal wall hernias.” Guidelines reflect the currently best available evidence in diagnostics and therapy and give recommendations to help surgeons to standardize their techniques and to improve their results. However, science is a dynamic field which is continuously developing. Therefore, guidelines require regular updates to keep pace with the evolving literature.

Methods

For the development of the original guidelines, all relevant literature published up to year 2012 was analyzed using the ranking of the Oxford Centre for Evidence-Based Medicine. For the present update, all of the previous authors were asked to evaluate the literature published during the recent years from 2012 to 2017 and revise their statements and recommendations given in the initial guidelines accordingly. In two Consensus Conferences (October 2017 Beijing, March 2018 Cologne), the updates were presented, discussed, and confirmed. To avoid redundancy, only new statements or recommendations are included in this paper. Therefore, for full understanding both of the guidelines, the original and the current, must be read. In addition, the new developments in repair of abdominal wall hernias like surgical techniques within the abdominal wall, release operations (transversus muscle release, component separation), Botox application, and robot-assisted repair methods were included.

Results

Due to an increase of the number of patients and further development of surgical techniques, repair of primary and secondary abdominal wall hernias attracts increasing interests of many surgeons. Whereas up to three decades ago hernia-related publications did not exceed 20 per year, currently this number is about 10-fold higher. Recent years are characterized by the advent of new techniques—minimal invasive techniques using robotics and laparoscopy, totally extraperitoneal repairs, novel myofascial release techniques for optimal closure of large defects, and Botox for relaxing the abdominal wall. Furthermore, a concomitant rectus diastasis was recognized as a significant risk factor for recurrence. Despite insufficient evidence with respect to these new techniques, it seemed to us necessary to include them in the update to stimulate surgeons to do research in these fields.

Conclusion

Guidelines are recommendations based on best available evidence intended to help the surgeon to improve the quality of his daily work. However, science is a continuously evolving process, and as such guidelines should be updated about every 3 years. For a comprehensive reference, however, it is suggested to read both the initial guidelines published in 2014 together with the update. Moreover, the presented update includes also techniques which were not known 3 years before.

Acute and chronic nicotine exposure differentially facilitate the induction of LTP

We report here that acute and chronic nicotine exposure facilitated the induction of long-term potentiation (LTP), a leading candidate for a cellular mechanism underlying learning and memory, in the hippocampus. Furthermore, acute application of nicotine in chronic nicotine-treated hippocampus further facilitated the induction of LTP, suggesting that acute and chronic nicotine effects on LTP induction are mediated by different mechanisms. These findings not only provide evidence for chronic nicotine-induced synaptic changes in the hippocampus, but also an explanation of the cellular basis of nicotine-induced cognitive enhancement.

Topography of Purkinje cell compartments and mossy fiber terminal fields in lobules II and III of the rat cerebellar cortex: spinocerebellar and cuneocerebellar projections

The cerebellar cortex is histologically uniform by conventional staining techniques, but contains an elaborate topography. In particular, on the efferent side the cerebellar cortex can be subdivided into multiple parasagittal compartments based upon the selective expression by Purkinje cell subsets of various molecules, for example the polypeptide antigens zebrin I and II, and on the afferent side many mossy fibers terminate as parasagittal bands of terminals. The relationships between mossy fiber terminal fields and Purkinje cell compartments are important for a full understanding of cerebellar structure and function. In this study the locations of spino- and cuneocerebellar mossy fiber terminal fields in lobules II and III of the rat cerebellum are compared to the compartmentation of the Purkinje cells as revealed by using zebrin II immunocytochemistry. Wheat germ agglutinin-horseradish peroxidase was injected at three different levels in the spinal cord and in the external cuneate nucleus, and the terminal field distributions in lobules II and III of the cerebellar cortex were compared with the Purkinje cell compartmentation. In the anterior lobe, zebrin II immunocytochemistry reveals three prominent, narrow immunoreactive bands of Purkinje cells, P1+ at the midline and P2+ laterally at each side. These are separated and flanked by wide zebrin- compartments (P1- and P2-). There are also less strongly stained P3+ and P4+ bands more laterally. The spinocerebellar terminals in the granular layer are distributed as parasagittally oriented bands. Projections from the lumbar region of the spinal cord terminate in five bands, one at the midline (L1), a second with its medial border midway across P1- and its lateral border at the P2+/P2- interface (L2), and a third extending laterally from midway across P2-. The lateral edge of L3 may align with the P3+/P3- border. The terminal fields labeled by a tracer injection into the thoracic region give a very similar distribution (T1, T2 and T3). The only systematic difference is in T2, which statistical analysis suggests may be broader than L2. In contrast, anterograde tracer injections into the cervical region label synaptic glomeruli scattered throughout the lobule with much weaker or no evidence of banding. The terminal fields of the cuneocerebellar projection have a complementary distribution to those of thoracic and lumbar spinocerebellar terminals. There are two lateral bands, Cu2 and Cu3. Cu2 lies within the Purkinje cell P1-compartment, abutting L1/T1 medially and L2/T2 laterally. Cu3 lies between L2 and L3 within the P2- Purkinje cell compartment. The medial edge of Cu3 is tightly aligned with the P2+/P2- border.(ABSTRACT TRUNCATED AT 400 WORDS)

Interleukin-6 levels in the conjunctival epithelium of patients with dry eye disease treated with cyclosporine ophthalmic emulsion

PURPOSE

To evaluate interleukin-6 (IL-6) levels in the conjunctival epithelium of patients with moderate to severe dry eye disease before and after treatment with cyclosporin A ophthalmic emulsion (CsA) or its vehicle.

METHODS

Conjunctival cytology specimens were obtained from a subset of patients enrolled in a 6-month randomized, double-masked clinical trial of the efficacy and safety of topical CsA at baseline and after 3 and 6 months of B.I.D. treatment with 0.05% cyclosporine emulsion (n = 13), 0.1% cyclosporine emulsion (n = 8), or vehicle (n = 10). RNA was extracted and a competitive reverse transcriptase polymerase chain reaction (RT-PCR) was used to evaluate the levels of mRNA encoding the inflammatory cytokine IL-6 and a housekeeping gene, G3PDH. Levels of IL-6 and G3PDH were measured and compared.

RESULTS

There was no change from baseline in the level of G3PDH after 3 or 6 months in any group. IL-6 normalized for G3PDH (IL-6/G3PDH ratio) was not different from baseline at 3 months but showed a significant decrease from baseline in the group treated with 0.05% CsA (p = 0.048) at 6 months. No significant between-group differences were noted and no correlation was observed between the change in IL-6/G3PDH and corneal fluorescein staining.

CONCLUSIONS

This preliminary, small-cohort study showed a decrease in IL-6 in the conjunctival epithelium of moderate to severe dry eye patients treated with 0.05% CsA for 6 months. The observed decrease suggests that dry eye disease involves immune-mediated inflammatory processes that may be decreased by treatment with topical ophthalmic cyclosporine.

No time to lose--high throughput screening to assess nanomaterial safety

Nanomaterials hold great promise for medical, technological and economical benefits. Knowledge concerning the toxicological properties of these novel materials is typically lacking. At the same time, it is becoming evident that some nanomaterials could have a toxic potential in humans and the environment. Animal based systems lack the needed capacity to cope with the abundance of novel nanomaterials being produced, and thus we have to employ in vitro methods with high throughput to manage the rush logistically and use high content readouts wherever needed in order to gain more depth of information. Towards this end, high throughput screening (HTS) and high content screening (HCS) approaches can be used to speed up the safety analysis on a scale that commensurate with the rate of expansion of new materials and new properties. The insights gained from HTS/HCS should aid in our understanding of the tenets of nanomaterial hazard at biological level as well as assist the development of safe-by-design approaches. This review aims to provide a comprehensive introduction to the HTS/HCS methodology employed for safety assessment of engineered nanomaterials (ENMs), including data analysis and prediction of potentially hazardous material properties. Given the current pace of nanomaterial development, HTS/HCS is a potentially effective means of keeping up with the rapid progress in this field--we have literally no time to lose.

Transforming growth factor beta-1 and beta-2 in human tear fluid

PURPOSE

To evaluate human tear fluid for transforming growth factor beta isoforms 1 and 2 (TGF-beta1 and TGF-beta2).

METHODS

To accomplish this, human tears were evaluated for TGF-betas by quantitative antibody sandwich ELISA (sELISA), mink lung epithelial cell (MLEC) growth inhibition bioassay and western blotting. Various physical and chemical treatments were used to activate TGF-beta in these assays.

RESULTS

TGF-betas could not be detected in untreated or heated tears by sELISA; however, mean TGF-beta1 concentrations of 2.32 ng/ml were detected in acid-activated tears by sELISA. Furthermore, 10.54 ng/ml of TGF-beta1 and 2.98 ng/ml of TGF-beta2 were detected in tears treated with the mucolytic agent, acetylcysteine. Total TGF-beta bioactivity in human tears measured by the MLEC assay was found to be 13.04 ng/ml in untreated tears and 24.85 ng/ml in acid-activated tears. Approximately one-half TGF-beta in tear specimens was biologically active (mean = 52%, range 39-71%). Total tear TGF-beta bioactivity could be completely neutralized by recombinant human TGF-beta1 latency associated peptide (rh TGF-beta1 LAP). Mean neutralization of tear TF-beta bioactivity was 83% by TGF-beta1-specific antisera, and was 13% by TBF-beta2-specific antisera. Immunoreactive TBF-beta bands at approximately 12.5 and 95 kD were observed in immunoblots of reduced acidified tears. A high molecular weight (MW) TGF-beta band (>203 dD) was noted in untreated tears; however, this band disappeared following treatment with acetylcysteine.

CONCLUSIONS

The results of these studies indicate that TGF-beta1 and TGF-beta2 are present in human tear fluid, and TGF-beta1 is the predominant isoform. There appear to be factors in human tears capable of binding TGF-beta.

Direct identification of a distinct site of interaction between the carboxyl-terminal residue of cholecystokinin and the type A cholecystokinin receptor using photoaffinity labeling

Mechanisms of ligand binding and activation of G protein-coupled receptors are particularly important, due to their ubiquitous expression and potential as drug targets. Molecular interactions between ligands and these receptors are best defined for small molecule ligands that bind within the transmembrane helices. Extracellular domains seem to be more important for peptide ligands, based largely on effects of receptor mutagenesis, where interference with binding or activity can reflect allosteric as well as direct effects. We now take the more direct approach of photoaffinity labeling the active site of the cholecystokinin (CCK) receptor, using a photolabile analogue of CCK having a blocked amino terminus. This probe, 125I-desaminotyrosyl-Gly-[Nle28,31, pNO2-Phe33]CCK-(26-33), binds specifically, saturably, and with high affinity (Ki = 3.3 nM) and has full agonist activity. This makes likely its being sited in a natural position within the receptor. As substrate, we used CHO-CCK receptor cells overexpressing functional recombinant rat type A CCK receptor. Covalent labeling of the appropriate Mr = 85,000-95,000 plasma membrane glycoprotein with core of Mr = 42,000 was established by SDS-polyacrylamide gel electrophoresis and autoradiography. A single domain adjacent to transmembrane 1 was labeled, as established by cyanogen bromide cleavage and separation by gel and/or high pressure liquid chromatography. The site of interaction was further defined by additional proteolysis with trypsin, with purification of the labeled fragment, followed by manual Edman degradation and radiochemical sequencing. This demonstrated that Trp39 was specifically labeled and likely resides proximate to the carboxyl-terminal pNO2-Phe33 residue of the probe. A model of this ligand-bound receptor has been constructed and will be used to plan future experiments to refine our understanding of this interaction.

Inactivation of alpha7 ACh receptors and activation of non-alpha7 ACh receptors both contribute to long term potentiation induction in the hippocampal CA1 region

Acute and chronic nicotine exposure differentially facilitate the induction of long-term potentiation (LTP), a synaptic model of learning and memory, in the hippocampal CA1 region. The mechanisms underlying these effects of nicotine, however, are unknown. In the present study, both nicotinic acetylcholine receptor (nAChR) agonists and an alpha7 nAChR antagonist facilitated the induction LTP in the hippocampal CA1 region of naive rat. Furthermore, chronic nicotine treatment lowered the threshold for induction of LTP, and acute application of nicotinic agonists, but not an alpha7 antagonist, further facilitated LTP induction in the chronic-nicotine-treated hippocampus. These results suggest not only that both activation of non-alpha7 nAChRs and inactivation of alpha7 nAChRs contribute to LTP induction, but also that chronic-nicotine-mediated facilitation of LTP induction is due to chronic-nicotine-induced desensitization of alpha7 nAChRs.

Alterations of ocular surface gene expression in Sjögren's syndrome

We have demonstrated that conjunctival epithelium of SS patients displays increased numbers of S-phase cells compared with non-dry eye controls. Moreover, in SS patients, these S-phase cells are distributed throughout all strata of the epithelium. The expression of MUC-1, a cell surface marker indicative of terminally differentiated epithelium, is localized to the conjunctival epithelial surface in SS and control patients. However, MUC-1 surface immunoreactivity appears to be reduced in SS epithelium, suggesting disruption of normal epithelial differentiation. A MUC-1 epitope exposed by pretreatment with neuraminidase is expressed in the basal and suprabasal layers of both patient populations. This antigen likely represents nascent, partially processed MUC-1(6) and may serve as a marker of the preterminally differentiated epithelial phenotype. Messenger RNA encoding several different inflammatory cytokines, including TNF-alpha, IL-1 alpha and beta, IL-6, IL-8, IL-10, and TGF-beta 1, is expressed at elevated levels within the conjunctival epithelium of SS patients compared with non-dry eye controls. Based on these observations, we have formulated a model to explain the ocular surface pathology of Sjögren's syndrome. We hypothesize that mechanical abrasion secondary to aqueous tear deficiency creates an inflammatory environment where conjunctival epithelial cells and lymphocytes are stimulated to produce and secrete various cytokines (i.e., IL-1, TNF-alpha, IL-6, IL-8, etc.) into the tear film. Elevated cytokine levels within the tear film, perhaps combined with reduced concentrations of essential lacrimal gland-derived factors (i.e., EGF, retinol), create an environment in which terminal differentiation of the ocular surface epithelium is impaired. As a consequence, the epithelium becomes hyperplastic, displaying increased mitotic activity, and loses the ability to express mature protective surface molecules including the membrane-bound mucin, MUC-1. This would imply that anti-inflammatory medications (i.e., corticosteroids or cyclosporine) that suppress the inflammatory component of this cascade may ameliorate the ocular surface disease and discomfort experienced by SS patients.

Direct identification of a second distinct site of contact between cholecystokinin and its receptor

We have developed a biologically active analogue of cholecystokinin (CCK) that incorporates a photolabile benzoylphenylalanine (Bpa) moiety in the middle of its pharmacophoric domain, which efficiently establishes a covalent bond with an interacting domain of the CCK receptor. This probe incorporated L-Bpa in the position of Gly29 of the well characterized, radioiodinatable CCK analogue, D-Tyr-Gly-[(Nle28,31)CCK-26-33]. It was a potent pancreatic secretagogue (EC50 = 28 +/- 6 nM) that was equally efficacious with natural CCK, and bound to the CCK receptor with moderate affinity (IC50 = 450 +/- 126 nM). This was adequate to allow specific covalent labeling of the receptor. The labeled domain was within the cyanogen bromide fragment of the receptor including the top of TM6 (the sixth transmembrane domain), the third extracellular loop, and TM7 (the seventh transmembrane domain), as proven by direct Edman degradation sequencing. When this fragment was modified by the replacement of Val342 with Met to generate an additional site of cyanogen bromide cleavage, the labeled fragment was reduced in apparent size consistent with its representing the carboxyl-terminal portion of this fragment. Radiochemical sequencing of that fragment demonstrated covalent attachment of the probe to His347 and Leu348 in this domain. This represents the second experimentally demonstrated contact between a CCK analogue and this receptor, complementing the labeling of the domain just above TM1 (the first transmembrane domain) by a photolabile residue at the carboxyl terminus of CCK (Ji, Z. S., Hadac, E. M., Henne, R. M., Patel, S. A., Lybrand, T. P., and Miller, L. J. (1997) J. Biol. Chem. 272, 24393-24401). Both contacts are consistent with the conformational model of CCK binding proposed on the basis of the initial contact.

The prediction of saliva swallowing frequency in humans from estimates of salivary flow rate and the volume of saliva swallowed

Saliva swallowing frequency is an important factor in models of oral clearance. It varies widely among individuals, and the basis for that variation has not been established. This study evaluated the use of unstimulated flow rate and the volume of saliva swallowed as predictors of swallowing frequency in 128 first-year dental students. A microphone was placed over the larynx, and swallowing activity was recorded for 30 min between 3-6:00 p.m. The average interval between swallows was determined, and individuals retained saliva in the mouth for a period equal to that time. Retained saliva was spat out, and volume was determined gravimetrically. Four replicate tubes were collected. Flow rate was determined as sample volume over average swallow time. A subset of 10 individuals was measured on two further occasions 2-3 months apart. An independent estimate of flow rate was taken on the second occasion. Repeat-measures analysis of variance and intraclass correlations were used to estimate the reproducibility of replicate volumes, and of measurements taken on different occasions. Associations between swallowing interval, saliva volume, and flow rate were evaluated by multiple regression. Replicate volumes were highly reproducible, as were measurements of volumes, swallow times, and flow rates on different occasions. Saliva volume and flow rate jointly accounted for 99% of variance in swallowing intervals. Swallowing intervals were shortest for individuals who combined high flow rates with small saliva volumes; current models suggest that their oral clearance might be most efficient. Swallowing intervals were longest for individuals with low flow rates and large volumes; their oral clearance might be the least efficient.

Vlugt TJ. Compressibility, thermal expansion coefficient and heat capacity of CH4 and CO2 hydrate mixtures using molecular dynamics simulations

Understanding the thermal and mechanical properties of CH₄ and CO₂ hydrates is essential for the replacement of CH₄ with CO₂ in natural hydrate deposits as well as for CO₂ sequestration and storage.

Production and secretion of transforming growth factor beta (TGF-beta) by the human lacrimal gland

PURPOSE

Transforming growth factor beta (TGF-beta) isoforms 1 and 2 have recently been detected in stimulated human tear fluid. The purpose of this study was to determine if these TGF-sbeta are produced and secreted by the lacrimal gland.

METHODS

To accomplish this, reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect expression of TGF-beta1 and TGF-beta2 mRNAs in normal human and rabbit lacrimal gland biopsies. Northern blot analyses were used for comparing the relative levels of expression of these TGF-beta mRNAs in rabbit lacrimal glands. Human lacrimal gland biopsies were evaluated by immunohistochemistry for production of TGF-beta1, TGF-beta1 latency associated peptide (LAP), and TGF-beta2 proteins. Supernatants of unstimulated and carbachol-stimulated human lacrimal gland explant cultures were evaluated for secretion of TGF-beta1 and TGF-beta2 by ELISA:

RESULTS

TGF-beta1 and TGF-beta2 mRNA expression was found in all human and rabbit lacrimal gland specimens by RT-PCR. A greater level of expression of TGF-beta1 than TGF-beta2 mRNA in the rabbit lacrimal gland was noted by Northern blot. In human lacrimal gland biopsies, TGF-beta1 and TGF-beta1 LAP were detected in acinar and ductal epithelia by immunohistochemistry. TGF-beta2 specific antibodies stained a small percentage of acinar and ductal epithelia, as well as material within the lumens of tubulo-acinar complexes in one-third of these glands. TGF-beta1 was detected in supernatants of human lacrimal gland explants, and the concentration of TGF-beta1 increased by an average of 280% after carbachol-stimulation (p = 0.004). TGF-beta2 could not be detected in unstimulated or stimulated human lacrimal gland supernatants.

CONCLUSIONS

The results of these experiments indicate that TGF-beta1 and TGF-beta2 are produced by and TGF-beta1 is secreted by the human lacrimal gland. They also suggest that the lacrimal gland may be one source of TGF-beta in human tear fluid.

Quantification of electroporative uptake kinetics and electric field heterogeneity effects in cells

We have conducted experiments quantitatively investigating electroporative uptake kinetics of a fluorescent plasma membrane integrity indicator, propidium iodide (PI), in HL60 human leukemia cells resulting from exposure to 40 mus pulsed electric fields (PEFs). These experiments were possible through the use of calibrated, real-time fluorescence microscopy and the development of a microcuvette: a specialized device designed for exposing cell cultures to intense PEFs while carrying out real-time microscopy. A finite-element electrostatic simulation was carried out to assess the degree of electric field heterogeneity between the microcuvette's electrodes allowing us to correlate trends in electroporative response to electric field distribution. Analysis of experimental data identified two distinctive electroporative uptake signatures: one characterized by low-level, decelerating uptake beginning immediately after PEF exposure and the other by high-level, accelerating fluorescence that is manifested sometimes hundreds of seconds after PEF exposure. The qualitative nature of these fluorescence signatures was used to isolate the conditions required to induce exclusively transient electroporation and to discuss electropore stability and persistence. A range of electric field strengths resulting in transient electroporation was identified for HL60s under our experimental conditions existing between 1.6 and 2 kV/cm. Quantitative analysis was used to determine that HL60s experiencing transient electroporation internalized between 50 and 125 million nucleic acid-bound PI molecules per cell. Finally, we show that electric field heterogeneity may be used to elicit asymmetric electroporative PI uptake within cell cultures and within individual cells.

Amplification of apoptosis through sequential caspase cleavage of the MET tyrosine kinase receptor

Activation of the MET tyrosine kinase receptor by hepatocyte growth factor/scatter factor is classically associated with cell survival. Nonetheless, stress stimuli can lead to a caspase-dependent cleavage of MET within its juxtamembrane region, which generate a proapoptotic 40 kDa fragment (p40 MET). We report here that p40 MET is in fact generated through an additional caspase cleavage of MET within its extreme C-terminal region, which removes only few amino acids. We evidenced a hierarchical organization of these cleavages, with the C-terminal cleavage favoring the juxtamembrane one. As a functional consequence, the removal of the last amino acids of p40 MET increases its apoptotic capacity. Finally, cells expressing a MET receptor mutated at the C-terminal caspase site are unable to generate p40 MET and are resistant to apoptosis, indicating that generation of p40 MET amplifies apoptosis. These results revealed a two-step caspase cleavage of MET resulting in the reshaping of this survival receptor to a proapoptotic factor.

A comparison of the cytogenetic alterations and global DNA hypomethylation induced by the benzene metabolite, hydroquinone, with those induced by melphalan and etoposide

Specific cytogenetic alterations and changes in DNA methylation are involved in leukemogenesis. Benzene, an established human leukemogen, is known to induce cytogenetic changes through its active metabolites including hydroquinone (HQ), but the specific alterations have not been fully characterized. Global DNA hypomethylation was reported in a population exposed to benzene, but has not been confirmed in vitro. In this study, we examined cytogenetic changes in chromosomes 5, 7, 8, 11 and 21, and global DNA methylation in human TK6 lymphoblastoid cells treated with HQ for 48 h, and compared the HQ-induced alterations with those induced by two well-known leukemogens, melphalan, an alkylating agent, and etoposide, a DNA topoisomerase II inhibitor. We found that rather than inducing cytogenetic alterations distinct from those induced by melphalan and etoposide, HQ induced alterations characteristic of each agent. HQ induced global DNA hypomethylation at a level intermediate to melphalan (no effect) and etoposide (potent effect). These results suggest that HQ may act similar to an alkylating agent and also similar to a DNA topoisomerase II inhibitor in living cells, both of which may be potential mechanisms of benzene toxicity. In addition to cytogenetic changes, global DNA hypomethylation may be another mechanism underlying the leukemogenicity of benzene.

Developing mossy fiber terminal fields in the rat cerebellar cortex may segregate because of Purkinje cell compartmentation and not competition

Many mossy fiber afferent projections to the rat cerebellar cortex terminate in parasagittal bands. In particular, the anterior lobe vermis of the cerebellum contains alternating bands of mossy fibers from the spinal cord and external cuneate nuclei. The cerebellar cortical efferents, the Purkinje cells, are also organized in parasagittal bands. These can be revealed by immunochemical staining for the antigen zebrin II, which is selectively expressed by bands of Purkinje cells. In some cases, the boundaries between mossy fiber terminal fields align with identified transitions between zebrin+/- sets of Purkinje cells, whereas others are located within apparently homogeneous Purkinje cell compartments. Two theories can explain the terminal-field topography: In one view, mossy fiber terminals segregate during development, because growth cones from different sources compete for common territory. Alternatively, mossy fiber growth cones directly recognize chemically distinct target territories, and activity-dependent mechanisms play only minor roles. To explore these issues, two sets of experiments were performed. First, the terminal-field map of the neonatal spinocerebellar projection was compared to the Purkinje cell compartmentation as revealed by anticalbindin immunocytochemistry. Second, subsets of spinocerebellar mossy fiber afferents were ablated early in postnatal development, and the consequences for the neighboring cuneocerebellar terminal fields were mapped in the adult with reference to the zebrin II+/- compartments. These experiments revealed no evidence that competitive interactions constrain the mossy fiber terminal-field distribution but, rather, suggest that the organization of the mossy fiber projections follows the compartmentation of the Purkinje cells.

A peptide agonist acts by occupation of a monomeric G protein-coupled receptor: dual sites of covalent attachment to domains near TM1 and TM7 of the same molecule make biologically significant domain-swapped dimerization unlikely

Membrane receptor dimerization is a well-established event for initiation of signaling at growth factor receptors and has been postulated to exist for G protein-coupled receptors, based on correction of nonfunctional truncated, mutant, or chimeric constructs by coexpression of appropriate normal complementary receptor domains. In this work, we have directly explored the molecular composition of the minimal functional unit of an agonist ligand and the wild-type G protein-coupled cholecystokinin (CCK) receptor, using photoaffinity labeling with a CCK analogue probe incorporating dual photolabile benzoylphenylalanine (Bpa) residues as sites of covalent attachment. This probe, 125I-D-Tyr-Gly-[(Nle28, 31, Bpa29,33)CCK-26-33], was shown to represent a full agonist and to specifically label the CCK receptor. Like probes incorporating individual photolabile residues in these positions,1,2 the two Bpa residues in the dual photoprobe covalently labeled receptor domains in the amino-terminal tail outside TM1 and in the third extracellular loop outside TM7. Absence of demonstrable receptor dimerization after the establishment of dual sites of covalent attachment supports the presence of these two domains within a single receptor molecule. Demonstration of the covalent adduct of a single probe molecule with the two cyanogen bromide fragments of the CCK receptor representing the expected domains further supports this interpretation. Thus, while domain-swapped dimerization of G protein-coupled receptors may be possible as a mechanism of rescue for nonfunctional molecules, it is not necessary for ligand binding and initiation of signaling at a wild-type receptor in this superfamily. The functional unit for CCK action is normally a ligand-receptor monomer.

Training-induced and electrically induced potentiation in the neocortex

Long-term potentiation (LTP) shares many properties with memory and is currently the most popular laboratory model of memory. Although it has not been proven that memory is based on an LTP-like mechanism, there is evidence that learning a motor skill can induce LTP-like effects. This evidence was obtained in a slice-preparation experiment, which precluded within-animal comparisons before and after training. In the present experiments, Long-Evans rats were unilaterally trained to acquire a forelimb reaching and grasping skill. Evoked potentials were found to be larger in motor cortex layer II/III in the trained, compared to the untrained, hemisphere in slice, acute, and chronic preparations. Consistent with previous research, the trained hemisphere was less amenable to subsequent LTP induction. Furthermore, the application of either LTP- or LTD-inducing stimulation during the training phase of the reaching task disrupted the acquisition of the skill, providing further evidence that memory may be based on an LTP mechanism.

Regulation of the Ets-1 transcription factor by sumoylation and ubiquitinylation

Sumoylation and ubiquitinylation reversibly regulate the activity of transcription factors through covalent attachment to lysine residues of target proteins. We examined whether the Ets-1 transcription factor is modified by sumoylation and/or ubiquitinylation. Among four potential SUMO motifs in Ets-1, we identified lysines 15 and 227 within the LK(15)YE and IK(227)QE motifs, as being the sumoylation acceptor sites. Using transfection of Ets-1 wildtype (WT) or its sumoylation deficient version (Ets-1 K15R/K227R), as well as WT or mutant proteins of the SUMO pathway, we further demonstrated that the E2 SUMO-conjugating enzyme Ubc9 and a E3 SUMO ligase, PIASy, can enhance Ets-1 sumoylation, while a SUMO protease, SENP1, can desumoylate Ets-1. We also found that Ets-1 is modified by K48-linked polyubiquitinylation independently of the sumoylation acceptor sites and is degraded through the 26S proteasome pathway, while sumoylation of Ets-1 does not affect its stability. Finally, sumoylation of Ets-1 leads to reduced transactivation and we demonstrated that previously identified critical lysine residues in Synergistic Control motifs are the sumoylation acceptor sites of Ets-1. These data show that Ets-1 can be modified by sumoylation and/or ubiquitinylation, with sumoylation repressing transcriptional activity of Ets-1 and having no clear antagonistic action on the ubiquitin-proteasome degradation pathway.