Preoperative systemic inflammation and perioperative myocardial injury: prospective observational multicentre cohort study of patients undergoing non-cardiac surgery.

BACKGROUND: Systemic inflammation is pivotal in the pathogenesis of cardiovascular disease. As inflammation can directly cause cardiomyocyte injury, we hypothesised that established systemic inflammation, as reflected by elevated preoperative neutrophil-lymphocyte ratio (NLR) >4, predisposes patients to perioperative myocardial injury. METHODS: We prospectively recruited 1652 patients aged ≥45 yr who underwent non-cardiac surgery in two UK centres. Serum high sensitivity troponin T (hsTnT) concentrations were measured on the first three postoperative days. Clinicians and investigators were blinded to the troponin results. The primary outcome was perioperative myocardial injury, defined as hsTnT≥14 ng L-1 within 3 days after surgery. We assessed whether myocardial injury was associated with preoperative NLR>4, activated reactive oxygen species (ROS) generation in circulating monocytes, or both. Multivariable logistic regression analysis explored associations between age, sex, NLR, Revised Cardiac Risk Index, individual leukocyte subsets, and myocardial injury. Flow cytometric quantification of ROS was done in 21 patients. Data are presented as n (%) or odds ratio (OR) with 95% confidence intervals. RESULTS: Preoperative NLR>4 was present in 239/1652 (14.5%) patients. Myocardial injury occurred in 405/1652 (24.5%) patients and was more common in patients with preoperative NLR>4 [OR: 2.56 (1.92-3.41); P<0.0001]. Myocardial injury was independently associated with lower absolute preoperative lymphocyte count [OR 1.80 (1.50-2.17); P<0.0001] and higher absolute preoperative monocyte count [OR 1.93 (1.12-3.30); P=0.017]. Monocyte ROS generation correlated with NLR (r=0.47; P=0.03). CONCLUSIONS: Preoperative NLR>4 is associated with perioperative myocardial injury, independent of conventional risk factors. Systemic inflammation may contribute to the development of perioperative myocardial injury. CLINICAL TRIAL REGISTRATION: NCT01842568.

Association between preoperative pulse pressure and perioperative myocardial injury: an international observational cohort study of patients undergoing non-cardiac surgery.

BACKGROUND: The management of elevated blood pressure before non-cardiac surgery remains controversial. Pulse pressure is a stronger predictor of cardiovascular morbidity in the general population than systolic blood pressure alone. We hypothesized that preoperative pulse pressure was associated with perioperative myocardial injury. METHODS: This is a secondary analysis of the Vascular Events in Non-cardiac Surgery Patients Cohort Evaluation (VISION) international cohort study. Participants were aged ≥45 yr and undergoing non-cardiac surgery at 12 hospitals in eight countries. The primary outcome was myocardial injury, defined using serum troponin concentration, within 30 days after surgery. The sample was stratified into quintiles by preoperative pulse pressure. Multivariable logistic regression analysis explored associations between pulse pressure and myocardial injury. We accounted for potential confounding by systolic blood pressure and other co-morbidities known to be associated with postoperative cardiovascular complications. RESULTS: One thousand one hundred and ninety-one of 15 057 (7.9%) patients sustained myocardial injury, which was more frequent amongst patients in the highest two preoperative pulse pressure quintiles {63-75 mm Hg, risk ratio (RR) 1.14 [95% confidence interval (CI): 1.01-1.28], P =0.03; >75 mm Hg, RR 1.15 [95% CI: 1.03-1.29], P =0.02}. After adjustment for systolic blood pressure, preoperative pulse pressure remained the dominant predictor of myocardial injury (63-75 mm Hg, RR 1.20 [95% CI: 1.05-1.37], P <0.01; >75 mm Hg, RR 1.25 [95% CI: 1.06-1.48], P <0.01). Systolic blood pressure >160 mm Hg was not associated with myocardial injury in the absence of pulse pressure >62 mm Hg (RR 0.67 [95% CI: 0.30-1.44], P =0.31). CONCLUSIONS: Preoperative pulse pressure >62 mm Hg was associated with myocardial injury, independent of systolic blood pressure. Elevated pulse pressure may be a useful clinical sign to guide strategies to reduce perioperative myocardial injury.

Preoperative heart rate and myocardial injury after non-cardiac surgery: results of a predefined secondary analysis of the VISION study.

BACKGROUND: Increased baseline heart rate is associated with cardiovascular risk and all-cause mortality in the general population. We hypothesized that elevated preoperative heart rate increases the risk of myocardial injury after non-cardiac surgery (MINS). METHODS: We performed a secondary analysis of a prospective international cohort study of patients aged ≥45 yr undergoing non-cardiac surgery. Preoperative heart rate was defined as the last measurement before induction of anaesthesia. The sample was divided into deciles by heart rate. Multivariable logistic regression models were used to determine relationships between preoperative heart rate and MINS (determined by serum troponin concentration), myocardial infarction (MI), and death within 30 days of surgery. Separate models were used to test the relationship between these outcomes and predefined binary heart rate thresholds. RESULTS: Patients with missing outcomes or heart rate data were excluded from respective analyses. Of 15 087 patients, 1197 (7.9%) sustained MINS, 454 of 16 007 patients (2.8%) sustained MI, and 315 of 16 037 patients (2.0%) died. The highest heart rate decile (>96 beats min(-1)) was independently associated with MINS {odds ratio (OR) 1.48 [1.23-1.77]; P<0.01}, MI (OR 1.71 [1.34-2.18]; P<0.01), and mortality (OR 3.16 [2.45-4.07]; P<0.01). The lowest decile (<60 beats min(-1)) was independently associated with reduced mortality (OR 0.50 [0.29-0.88]; P=0.02), but not MINS or MI. The predefined binary thresholds were also associated with MINS, but more weakly than the highest heart rate decile. CONCLUSIONS: Preoperative heart rate >96 beats min(-1) is associated with MINS, MI, and mortality after non-cardiac surgery. This association persists after accounting for potential confounding factors. CLINICAL TRIAL REGISTRATION: NCT00512109.

Preoperative renal dysfunction and mortality after non-cardiac surgery.

BACKGROUND: Chronic kidney disease is an important preoperative risk factor. However, the association between renal dysfunction and risk of death has not been well explored in non-cardiac surgery. METHODS: Two prospective observational studies in non-cardiac surgery were analysed: the European Surgical Outcomes Study (EuSOS) and the UK National Confidential Enquiry into Patient Outcome and Death (NCEPOD). The relationship between preoperative estimated glomerular filtration rate (eGFR) and postoperative mortality was examined using multivariable Cox proportional hazards models. RESULTS: In EuSOS, 1580 (4·3 per cent) of 36 779 patients died in hospital; in NCEPOD, 298 (2·8 per cent) of 10 466 patients had died by 60 days after surgery. Chronic kidney disease (eGFR below 60·0 ml per min per 1·73 m(2) ) was present in 6415 patients (17·4 per cent) in EuSOS and 2262 (21·6 per cent) in NCEPOD. Preoperative chronic kidney disease was associated with older age, men, diagnosis of diabetes, cardiovascular or respiratory disease, and non-elective surgery. Preoperative eGFR categories below 60·0 ml per min per 1·73 m(2) were associated with increasing adjusted hazard ratios (HRs) for death compared with a value of 90·0 ml per min per 1·73 m(2) and above. In EuSOS, the risk of death increased with lower eGFR category, to a maximum with eGFR 15·0-29·9 ml per min per 1·73 m(2) (HR 3·37, 95 per cent c.i. 2·70 to 4·22). In NCEPOD, the risk of death also increased with declining eGFR and was maximal for eGFR below 15·0 ml per min per 1·73 m(2) (HR 3·40, 1·78 to 6·50). CONCLUSION: Renal dysfunction is an important risk factor for death after non-cardiac surgery and the risk increases steeply for patients with moderate to severe kidney dysfunction.

The effects of stress on alcohol consumption: mild acute and sub-chronic stressors differentially affect apomorphine susceptible and unsusceptible rats.

The aim of this study was to investigate the effects of mild acute and mild sub-chronic challenges on alcohol intake and preference in the genetically selected ratlines of apomorphine susceptible (APO-SUS) and apomorphine unsusceptible (APO-UNSUS) animals. Animals from both lines were subjected to the 24 hr continuous alcohol vs. water paradigm under baseline conditions, after a single stressor and after multiple stressors. The intake of alcohol in ml was measured and converted to two values, namely intake in g/kg/24 hour of, and preference for, alcohol. This study shows that under baseline conditions the APO-UNSUS animals consume/prefer more alcohol than the APO-SUS animals. After an acute challenge the APO-SUS animals show a large increase in consumption, whereas the APO-UNSUS animals display only a small increase. Furthermore, sub-chronic challenges can further increase the consumption of the APO-UNSUS rat, but not that of the APO-SUS rat. The APO-SUS/ APO-UNSUS rats represent a good model to study the interaction between genetic factors and stress on directing alcohol consumption.

Comparison of Propofol-Lipuro with propofol mixed with lidocaine 10 mg on propofol injection pain.

A common drawback of propofol is pain on injection and lidocaine is commonly mixed with propofol to reduce its incidence and severity. We conducted a randomised, prospective, double-blind study to compare injection pain following the administration of two different formulations of propofol in 200 unpremedicated ASA I-III adult patients scheduled for elective surgery under general anaesthesia. Patients were allocated randomly into two groups to receive either Propofol-Lipuro without added lidocaine or Diprivan mixed with lidocaine 10 mg. Five ml of the study solution was injected at a constant rate over 15 s and patients graded any associated pain or discomfort using a four-point verbal rating scale. The incidence of propofol injection pain was virtually identical in both study groups with 37/98 (38%) patients experiencing pain or discomfort following Propofol-Lipuro compared with 35/98 (36%) after Diprivan (p = 0.88). We observed no significant difference in pain scores between the groups (p = 0.67). Moderate or severe injection pain was experienced by 12/98 (12%) patients given Propofol-Lipuro compared with 8/98 (8%) given Diprivan (p = 0.48).

Helicobacter pylori infection is not associated with diabetes mellitus, nor with upper gastrointestinal symptoms in diabetes mellitus.

OBJECTIVE: The association between Helicobacter pylori (H. pylori) infection and diabetes mellitus is controversial. We aimed to determine the prevalence of H. pylori infection in patients with diabetes and nondiabetic controls, and assess whether H. pylori infection was associated with upper gastrointestinal (GI) symptoms in diabetes mellitus. METHODS: A total of 429 patients with type 1 (n = 49) or type 2 (n = 380) diabetes mellitus (48.6% women, mean age 60.7 yr) and 170 nondiabetic controls (34.7% women, mean age 60.4 yr) were evaluated. All subjects completed a validated questionnaire (the Diabetes Bowel Symptom Questionnaire) to determine upper GI symptoms, and a blood sample was tested for H. pylori infection using a validated ELISA kit (sensitivity 96%, specificity 94%). RESULTS: Seroprevalence of H. pylori was 33% and 32%, respectively, in patients with diabetes and controls (NS). In both groups, the seroprevalence was significantly higher in men than in women; 39% vs 25% (p = 0.002) in diabetic patients, and 40% vs 20% (p = 0.01) in controls. Patients with diabetes had a significantly higher prevalence of early satiety (OR = 2.30), fullness (OR = 3.15), and bloating (OR = 1.50) compared with controls. Upper GI symptoms were present in 49% of H. pylori-positive and 53% of H. pylori-negative patients with diabetes (OR = 0.87, 95% CI 0.58-1.31, p = 0.56). H. pylori infection was also not associated with any of the individual upper GI symptoms before or after adjustment for potential confounding factors. However, patient age and female gender were identified as independent risk factors for upper GI symptoms. Smoking was a risk factor for bloating and early satiety. CONCLUSIONS: H. pylori infection appears not to be associated with diabetes mellitus or upper GI symptoms in diabetes mellitus.

Survey of patient satisfaction in adult psychiatric outpatient clinics.

A client satisfaction survey was undertaken in two adult psychiatric outpatient clinics. The anonymous self-report questionnaire covering demographic, setting and satisfaction with service variables was endorsed by 203 participants. The mean age of the subjects was 42.5 +/- 19 years, with a small majority (58.6%) of females. Overall satisfaction with psychiatric care was high (79.8%). None of the demographic or setting variables correlated significantly with satisfaction. Psychoeducation was significantly correlated with level of satisfaction with services. These findings further emphasize the importance of psychoeducation by service providers in mental health.

The role of trophoblast in the physiological change in decidual spiral arteries.

The remodelling of the maternal uterine spiral arteries during pregnancy, known as physiological change, is critical for the normal growth and development of the fetus. Controversy has surrounded the part played by fetal trophoblast in the transformation of these spiral arteries. To address this debate, a histological and immunochemical comparison of blood vessels from the implantation sites of human pregnancies of early gestation with uterine tissue where trophoblast was absent was performed. Results showed that true physiological change, with the features of medial necrosis and deposition of fibrinoid material, only occurred in the presence of trophoblast. In addition, it was found that subpopulations of trophoblast contribute differently in the process. Interstitial trophoblast-mediated destruction of the arterial media precedes replacement of the endothelial cells by endovascular trophoblast.

Neutrophil elastase cleavage of human factor IX generates an activated factor IX-like product devoid of coagulant function.

In preliminary studies, the generation of thrombin in vivo was found to induce a 92% loss of functional activity of factor IX (F.IX) despite the detection by Western blotting of a product resembling activated F.IX (F.IXa) and a 25% increase in F.IX antigen levels (Hoogendoorn et al, Thromb Haemost 69:1127, 1993 [abstr]). These changes were associated with evidence of increased elastase availability. To study the possibility that these two observations were related, a detailed physical and functional characterization of the hydrolysis of purified human F.IX by human neutrophil elastase (HNE) was performed in vitro. An activated partial thromboplastin time (aPTT) clotting assay demonstrated that, although HNE eliminated the potential of F.IX to be activated, it only marginally reduced the F.IXa activity. Reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that HNE treatment of F.IX generated cleavage products of 30 and 20 kD that could not be distinguished from the respective heavy and light chain peptides that were identified in parallel studies when F.IX was activated by activated bovine F.XI (F.XIa), one of its physiological activators. In addition, nonreducing SDS-PAGE demonstrated that HNE-treated F.IX formed no complexes with antithrombin III (ATIII) in the presence of heparin. Furthermore, HNE-treated F.IX was unable to (1) bind the active site probe p-aminobenzamidine; (2) hydrolyze the synthetic peptide substrate CH3SO2-Leu-Gly-Arg-p-nitroanilide; and (3) activate human factor X (F.X). In contrast to dansyl-Glu-Gly-Arg-chloromethyl ketone (dEGR)-inactivated F.IXa, HNE-treated F.IX (0.01 to 10,000 pmol/L) failed to inhibit the clotting activity of F.IXa (10 pmol/L) in the aPTT. NH2-terminal sequencing indicated that HNE cleaved human F.IX at Thr140, Thr144, Ile164, Thr172, and Val181. The cleavages at Thr140/Thr144 and at Thr172/Val181 are both very close to the normal F.XIa alpha-(Arg145) and beta-(Arg180) cleavage sites, respectively. In summary, the results suggest that the activatability of F.IX is eliminated after cleavage by HNE and that the inability of HNE-treated F.IX to support F.IXa-like coagulant function is a consequence of improper active site formation. These in vitro observations support the possibility that increased HNE cleavage of F.IX in vivo may contribute to the disregulation of hemostasis that occurs in conditions such as disseminated intravascular coagulation (DIC).

The likely implications of the 1997 Coroners Ordinance on the autopsy service of a teaching hospital.

The new Hong Kong Coroners Ordinance was published in April 1997. It introduced an expanded set of guidelines for reporting deaths to the coroner as well as the threat of criminal proceedings for non-compliance. The Ordinance is due to be implemented in early 1998. The aim of this study is to determine the likely effect of the new law on the relative proportion of coroner's and hospital (consent) autopsies. A total of 352 consecutive autopsy cases were reviewed; 170 (48.3%) were referred for coroner's autopsies and 182 (51.7%) for hospital autopsies. But applying the criteria of the current ordinance, there should have been 213 (60.5%) coroner's cases and 139 (39.5%) hospital autopsies-that is, 43 hospital autopsies should have been coroner's autopsies. Under the new Coroners Ordinance, there would be 300 (85.2%) coroner's autopsies and only 52 (14.8%) hospital autopsies. The new Coroners Ordinance is likely to result in a greater number of requests for coroner's autopsies with a corresponding decline in hospital autopsies---in our case, a shift from 48.3% of all autopsies performed to 85.2%! This increase would be due largely to the requirement for reporting stillbirths but would also be due to increased reporting for fear of 'criminal proceedings' for non-compliance. An absolute increase in the number of autopsies is also anticipated, although the magnitude cannot as yet be predicted.

Protein phosphatase activity in human keratinocytes cultured from normal epidermis and epidermis from patients with harlequin ichthyosis.

We investigated serine/threonine protein phosphatase (PP) activity and the expression of PP2A during growth and differentiation of epidermal keratinocytes in culture. Keratinocyte PP activity was strongly inhibited by calyculin A and okadaic acid, indicating that the activity was mainly due to PP2A and PP1. The phosphatase activity decreased to about 20% of the initial (day 1) level by the time of confluence and to about 10% at day 7 postconfluence. In contrast to activity, the level of expression of the PP2A catalytic subunit protein and the mRNA for the two isoforms increased slightly over the period of growth. Keratinocyte differentiation was shown by a significant increase in profilaggrin expression after confluence. Keratinocytes were also cultured from individuals affected with harlequin ichthyosis. This severe hyperkeratotic skin disorder has abnormal lipid structures and is blocked in the PP2A-dependent conversion of phosphorylated profilggrin to the non-phosphorylated filaggrin. The PP activity in harlequin cultures was lower than in normal cultures (about 20% of the subconfluent normal control value) and decreased even further in confluent cultures. In contrast, the level of expression of the PP2A catalytic subunit protein and mRNA for the two isoforms was similar to that of normal keratinocytes and increased with confluence. These results suggest that PP activity in keratinocytes is regulated in a post-translational manner; they also support the possibility of impaired or reduced function of PPs in harlequin ichthyosis.

Harlequin ichthyosis. Variability in expression and hypothesis for disease mechanism.

BACKGROUND: Harlequin ichthyosis is an inherited skin disorder that usually results in death shortly after birth. Although the clinical features of this disorder are well described, the underlying molecular basis is not understood. In this article, we discuss the results of the latest histologic, immunochemical, and Western immunoblotting studies done in our laboratory and propose a hypothesis for molecular basis of this disorder. OBSERVATIONS: Previous experiments done in our laboratory show suggestive evidence for defective lipid synthesis and protein dephosphorylation in harlequin ichthyosis. Our latest study shows that the catalytic subunit of one of the most prevalent protein phosphatase, type 2A protein phosphatase, appears to be altered in some cases of type 2 harlequin ichthyosis. CONCLUSIONS: Based on these observations and the known functions of protein phosphatase in keratinocytes, we hypothesize that the underlying molecular basis of harlequin ichthyosis may be related to mutations affecting protein dephosphorylation. We further describe approaches by which this hypothesis can be tested.

Identification of rat epidermal profilaggrin phosphatase as a member of the protein phosphatase 2A family.

The aggregation of cellular intermediate filaments is an important step in the terminal differentiation of keratinocytes. It has been shown that epidermal filaggrin can cause intermediate filaments to aggregate in vitro and may also have the same function in vivo. Filaggrin is derived via dephosphorylation and proteolysis from a highly phosphorylated precursor, profilaggrin, which is found in the granular layer of the epidermis. Using casein kinase II phosphorylated filaggrin as substrate, a profilaggrin phosphatase has been partially purified from rat epidermal homogenate by three chromatographic steps (DE52, hydroxylapatite and S200 gel filtration). Profilaggrin phosphatase activity eluted from the last column has a Km of 0.12 mM and a Vmax of 8 nmol/mg/min with respect to phosphofilaggrin. Results obtained by initial rate analysis showed that the enzymatic activity is not affected by phospho-tyrosyl phosphatase inhibitors and the active fractions preferentially dephosphorylate the alpha subunit of phosphorylase kinase which has been phosphorylated by cAMP-dependent kinase. These results suggest that epidermal profilaggrin phosphatase is not a phospho-tyrosyl phosphatase or a type 1 phospho-seryl/phospho-threonyl phosphatase. Dephosphorylation is not affected by EDTA, calcium or magnesium, but is very sensitive to okadaic acid inhibition (IC50 = 80 pM), suggesting that the enzymatic activity is related to that of the protein phosphatase 2A (PP2A).(ABSTRACT TRUNCATED AT 250 WORDS)

Disposition and orientation of ductin (DCCD-reactive vacuolar H(+)-ATPase subunit) in mammalian membrane complexes.

The disposition and orientation of mouse ductin (the subunit c of the vacuolar H(+)-ATPase) in gap junctions has been examined. Like the Nephrops norvegicus (arthropod) form, mouse ductin in the intact junctional structure is resistant to high levels of nonspecific proteinase, suggesting that it is for the most part buried in the bilayer. Antisera to an octapeptide near the N-terminus cross-react with ductins in gap junction preparations from four different mouse tissues, from chicken and Xenopus laevis liver, and from N. norvegicus hepatopancreas. The antisera and antibodies, affinity purified against the octapeptide, agglutinate isolated gap junctions, suggesting that the N-terminus is located on the exposed surface, equivalent to the cytoplasmic face of an intercellular gap junction. The antibodies also block dye coupling when injected into cells in culture, confirming the cytoplasmic location of the epitope. The lipophylic reagent dicylohexyl carbodiimide (DCCD), which targets carboxyl groups within the membrane and selectively reacts with ductin in N. norvegicus gap junction preparations, rapidly inhibits junctional communication. Bafilomycin A1, which inhibits V-ATPase and stops vacuolar acidification, does not affect dye coupling, showing that the inhibition seen with antibodies and DCCD is not an indirect consequence of their action on the ductin of V-ATPase. Consistent with this interpretation the anti-peptide antibodies do not bind to intact chromaffin granules or inhibit their V-ATPase activity, but do bind to osmotically disrupted granule membrane. This suggests that ductin has an orientation (N-terminus pointing away from the cytoplasm) in the vacuolar membrane opposite to that in the gap junction membrane.

Communication compartments in hair follicles and their implication in differentiative control.

Observations on hair follicles presented in this paper show that boundaries to junctional communication are formed between groups of cells following different pathways of differentiation. The patterns of junctional communication in the bulbs of rat vibrissa follicles and human hair follicles were studied by microinjection of the fluorescent tracer dye Lucifer Yellow CH. Dye spread was extensive between undifferentiated cells of the hair bulb matrix but communication boundaries were found between groups of morphologically distinct cells. For example, boundaries to dye spread were observed between undifferentiated matrix cells and cells in the early stage of differentiation into the inner root sheath, between Huxley's and Henle's layers in the early inner root sheath and between cells of the cuticle and cortex of the hair. Dye did not spread between epithelial cells of the hair bulb and mesenchymal cells of the connective tissue sheath or dermal papilla. The patterns of dye spread became more complex (increased boundary formation and subcompartmentation) as differentiation progressed in higher regions of the hair bulb. The observed communication can be related to previous ultrastructural studies by others on the distribution of gap junctions in the wool follicle. These results show that junctional communication, with its consequent intercellular spread of small ions and molecules, is associated with uniformity of expression and behaviour within cell populations and that interruption of communication through the formation of boundaries and communication compartments is temporally and spatially related to the production of subpopulations of cells committed to the expression of different phenotypes.

Tissue-specific regulation of junctional communication in the skin of mouse fetuses homozygous for the repeated epilation (Er) mutation.

Mouse embryos homozygous for the repeated epilation (Er) gene have abnormally developed skin characterised by hyper-proliferation and incomplete differentiation of the epidermis. In this report, we have studied the patterns of junctional communication in the skin of these mutants to see if the loss of control of proliferation/differentiation is associated with any altered patterns of communication. Using the dye-injection technique we have shown that, compared to normal skin, junctional communication among dermal cells of Er/Er mutants is greatly reduced and the frequency of dermal-epidermal communication is, on the other hand, increased. These results support our previously proposed model, which suggests that selective regulation of junctional communication can be a component of proliferative control in a complex tissue.

Junctional communication and cellular differentiation.

Gap junctions provide pathways of direct cell to cell communication in the tissues of metazoan animals. Cells joined by gap junctions share their small ions and molecules but can maintain distinctive activities through expression of different macromolecules which are too large to pass through the junctions. The junctional channels are made of a tissue invariant, evolutionarily conserved 16-18 k protein but the formation and maintenance of active coupling also requires one or more connexins, a family of tissue-specific proteins ranging in size from 21 k to 70 k. Junctions can be isolated as complexes containing both types of protein by mild procedures using high pH but the connexins can be removed by detergent, urea and protease treatment without destroying the characteristic junctional-morphology of hexagonally packed channels in the double membrane structures. There is also some evidence for the participation in the complex of tissue-specific proteoglycans which perhaps interact with the tissue-specific connexins and account for specificity of junction formation. Such specificity in mixed cultures leads to the production of communication compartments, groups of cells joined by junctions but separated by reduced trans-boundary coupling from cells in adjacent compartments. Compartmentation also occurs in vivo resulting in specific patterns of junctional communication which have been mapped in most detail in mouse skin. These mapping data and the changes which are associated with abnormal proliferation have lead to new ideas on intercellular control.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the tumour promoter 12-O-tetradecanoylphorbol-13-acetate on junctional communication in intact mouse skin: persistence of homologous communication and increase of epidermal-dermal coupling.

12-O-Tetradecanoylphorbol-13-acetate (TPA) has been reported to inhibit junctional communication in some cell cultures. In view of the tumour-promoting activity of TPA in rodent skin, these results have interesting implications for the possible role of junctional communication in tumorigenesis. However, little is known about the effect of TPA on junctional communication in intact skin. Using the technique of iontophoretic injection of Lucifer Yellow CH, we have now studied the patterns of junctional communication in skin treated with TPA. In this paper we report results of such experiments showing that junctional communication in skin persists 4 h after treatment with TPA. In addition, TPA unexpectedly increases communication across the dermal-epidermal boundary. These effects of TPA can still be observed 24 h after treatment. In light of these results, we discuss the possible role of junctional communication in the control of proliferation of normal and pathological tissues.

Patterns of junctional communication in skin: studies on cultured keratinocytes.

Junctional communication has long been suggested to play a role in coordinating the development of multicellular tissues. A better understanding of the patterns of communication between cells in such tissues is important for the identification of areas where this process may have a role. We have investigated the patterns of communication in cultures of human epidermal keratinocytes by iontophoretic injection of Lucifer Yellow CH, using involucrin expression as a marker of cells undergoing terminal differentiation. Cells that lack involucrin (i.e., the basal, proliferating cells) transfer dye preferentially to other involucrin-negative cells, whereas involucrin-positive cells either are not coupled or transfer dye with similar frequency to involucrin-positive and involucrin-negative neighbors. This decrease in communication associated with terminal differentiation was observed in both the presence and the absence of assembled desmosomes. Our observations lead us to speculate that loss of junctional communication may influence the commitment of basal keratinocytes to terminal differentiation.