Risk Assessment Model for Postpartum Venous Thromboembolism Prevention in Patients with Systemic Lupus Erythematosus

OBJECTIVE

This article assesses the application of the Royal College of Obstetricians and Gynaecologists (RCOG) venous thromboembolism (VTE) risk model on a cohort of postpartum patients with a history of systemic lupus erythematosus (SLE).

STUDY DESIGN

This is a secondary analysis of an ongoing patient registry of women with SLE from 2016 to 2022. There were 49 SLE patients with 55 pregnancies using the Definitions of Remission in SLE (DORIS) criteria to determine SLE disease activity. RCOG risk assessment model scoring was calculated for each patient prior to and after delivery. The primary outcome was the qualification of "active SLE" by standard rheumatologic criteria and assessment of recommendations for VTE prophylaxis based on RCOG VTE risk assessment scoring. Data were analyzed using Fisher's exact test, chi-square test, and Mann-Whitney U test with significance defined as p < 0.05.

RESULTS

In the study cohort, 34 pregnancies (61.8%) were in DORIS remission at delivery. Twenty-one pregnancies (38.2%) were not and scored 3 points on the RCOG VTE risk model. Of these pregnancies, only 19% (n = 4) were recommended for VTE prophylaxis by the obstetrical provider despite RCOG score ≥3. Only 35.7% (n = 5) of pregnancies in DORIS remission, but with 3 points for non-SLE-related VTE risk factors (n = 14), were recommended for VTE prophylaxis. Of the 20 pregnancies in remission with an RCOG score < 3 after assessing all risk factors, 15% (n = 3) were nevertheless recommended for VTE prophylaxis. No patients had a postpartum VTE regardless of therapy.

CONCLUSION

These data reveal a need to improve upon providing postpartum VTE prophylaxis to SLE patients not in remission while also recognizing a diagnosis of SLE alone should not equate with active disease. Moreover, SLE patients in remission may still warrant VTE prophylaxis if other non-SLE-related risk factors are present.

KEY POINTS

· Those with SLE are at increased risk for VTE postpartum.. · VTE prophylaxis should be instituted when clinically appropriate.. · Caution should be exercised in broadly assigning disease activity for SLE diagnosis only.. · This study supports VTE prophylaxis use in postpartum patients with SLE..

Comparing outcomes of fetal growth restriction defined by estimated fetal weight versus isolated abdominal circumference

PURPOSE

The objective of this study was to compare maternal and neonatal outcomes when the diagnosis of FGR was based on isolated abdominal circumference < 10th percentile for gestational age (GA) (iAC group) versus overall estimated fetal weight < 10th percentile (EFW group).

METHODS

This was a retrospective cohort study of singleton gestations who underwent growth ultrasounds and delivered at a single health system from 1/1/19-9/4/20. The study group was comprised of patients with AC < 10th percentile and EFW ≥ than the 10th percentile (iAC group). The control group included patients with overall EFW < 10th percentile (EFW group). Outcomes evaluated included GA at delivery, mode of delivery, fetal and neonatal outcomes. Data was analyzed using Mann Whitney U, X2, and Fisher exact tests with significance defined as p < 0.05.

RESULTS

635 women met the inclusion criteria, 259 women in the iAC group and 376 women in the EFW group. The iAC group was noted to have a later GA at diagnosis and delivery. iAC was associated with lower rates of preterm birth (PTB), NICU admission, SGA at delivery and umbilical artery cord gas < 7.0.

CONCLUSION

Using iAC as a definition of FGR increased the number of FGR cases by 1.69-fold over EFW criteria alone. However, obstetrical and neonatal outcomes for the iAC group appear to be significantly better than those in the EFW group, with low rates of PTB, NICU admission, and umbilical artery cord gas < 7.0.

Postpartum Readmissions for Hypertensive Disorders in Pregnancy During the COVID-19 Pandemic

BACKGROUND

Hypertensive disorders in pregnancy are one of the most common causes of readmission in the postpartum period. Because of the COVID-19 pandemic, early hospital discharge was encouraged for patients who were medically stable, because hospitalization rates among SARS-CoV-2–infected patients steadily increased in 2020. The impact of an early discharge policy on postpartum readmission rates among patients with hypertensive disorders in pregnancy is unknown.

OBJECTIVE

This study aimed to compare the postpartum readmission rates of patients with hypertensive disorders in pregnancy before and after implementation of an early discharge policy owing to the COVID-19 pandemic.

STUDY DESIGN

This was a quality improvement, retrospective cohort study of postpartum patients with antenatal hypertensive disorders in pregnancy who delivered and were readmitted because of hypertensive disorders in pregnancy at the New York University Langone Health medical center from March 1, 2019 to February 29, 2020 (control cohort) and from April 1, 2020 to March 31, 2021 (COVID-19 cohort). During the pandemic, our institution introduced an early discharge policy for all postpartum patients to be discharged no later than 2 days postpartum during the delivery admission if deemed medically appropriate. The reduction in postpartum length of stay was accompanied by the continuation of patient education, home blood pressure monitoring, and outpatient follow-up. The primary outcome was the comparison of the readmission rates for patients with postpartum hypertensive disorders in pregnancy. Data were analyzed using Fisher's Exact tests, chi-square tests, and Wilcoxon rank-sum tests with significance defined as P<.05.

RESULTS

There was no statistical difference in the readmission rates for patients with postpartum hypertensive disorders in pregnancy before vs after implementation of an early discharge policy (1.08% for the control cohort vs 0.59% for the COVID-19 cohort). The demographics in each group were similar, as were the median times to readmission (5.0 days; interquartile range, 4.0–6.0 days vs 6.0 days; interquartile range, 5.0–6.0 days; P=.13) and the median readmission length of stay (3.0 days; interquartile range, 2.0–4.0 days vs 3.0 days; interquartile range, 2.0–4.0 days; P=.45). There was 1 intensive care unit readmission in the COVID-19 cohort and none in the control cohort (P=.35). There were no severe maternal morbidities or maternal deaths.

CONCLUSION

These findings suggest that policies calling for a reduced postpartum length of stay, which includes patients with hypertensive disorders in pregnancy, can be implemented without impacting the hospital readmission rate for patients with hypertensive disorders in pregnancy. Continuation of patient education and outpatient surveillance during the pandemic was instrumental for the outpatient postpartum management of the study cohort. Further investigation into best practices to support early discharges is warranted.

Coexistent trichilemmoma and trichoblastoma without associated nevus sebaceus

Trichilemmoma and trichoblastoma are benign adnexal neoplasms derived from the hair follicle unit. While trichilemmomas are closely associated with the epidermis, trichoblastomas are found within the dermis and subcutaneous tissue. Both tumors have been reported to arise within nevus sebaceus of Jadassohn (NSJ). We present a 42-year-old white male with a 5 mm crusted, erythematous papule on the right occipital scalp that had been present for years. A shave biopsy was performed and read as trichilemmoma involving the biopsy base. The patient returned for follow-up 2 months later with recurrence of a crusted papule, measuring 9 mm in greatest diameter at the site of the previous biopsy. The lesion was excised for complete histologic evaluation, diagnosed as trichilemmoma with verrucoid features and associated basaloid proliferation with adnexal differentiation, again involving the biopsy base. The lesion recurred 2 months later in the form of an 8 mm multilobulated pink nodule. It was again excised and diagnosed as trichoblastoma with overlying trichilemmoma. The significance of this finding is that coexistent lesions do not necessarily necessitate a preexisting nevus sebaceous. Rather, this finding supports the notion of a common stem cell capable of differentiating toward the various portions of the hair follicle unit and adnexal structures. The idea is that any portion of the skin adnexal structure may develop out of a pluripotential germ cell and develop into a tumor.

Loss of Bcl-2 expression in Barrett's dysplasia and adenocarcinoma is associated with tumor progression and worse survival but not with response to neoadjuvant chemoradiation

Esophageal adenocarcinoma arising on a background of Barrett's esophagus is increasing in incidence. A molecular understanding of both the progression of Barrett's esophagus and the factors determining the response of adenocarcinoma to neoadjuvant therapy is required, and this study focused on the role of proteins regulated by the bcl-2 family of genes, which are important regulators of programmed cell death (apoptosis). In total, 48 patients (36 men, 12 women) with Barrett's adenocarcinoma were studied. All patients received preoperative chemoradiotherapy followed by surgery. Bcl-2, bax and bcl-x protein expression were detected by standard avidin-biotin peroxidase method. Bcl-2, bax and bcl-x expression were detected in 84%, 80%, and 76%, respectively, of normal squamous mucosa. An increasing degree of dysplasia in Barrett's mucosa both before and after chemoradiotherapy was significantly associated with a reduction of bcl-2 expression (P = 0.03 and 0.009, respectively). Bcl-2 expression was significantly associated with tumor differentiation (P = 0.03) and a trend towards earlier T stage (P = 0.08), but not with nodal status. Pre-therapeutic bcl-2, bax and bcl-x protein expression (27%, 75%, and 87.5%, respectively) were not associated with tumor response or resistance to therapy. Bcl-2-positive patients had a significantly improved survival compared with bcl-2-negative tumors. A significant reduction of bcl-2 expression is associated with the progression of Barrett's mucosa to adenocarcinoma. Bcl-2 expression was associated with improved survival. Preoperative chemoradiotherapy induces expression of bax and bcl-x protein. The pretreatment expression of bcl-2 and related proteins did not predict response or resistance to neoadjuvant chemoradiotherapy, suggesting that regulators of apoptosis alone do not determine the response of Barrett's adenocarcinoma to neoadjuvant therapy.

Role of Mimeticism and Spatiality in Textual Recall

Four experiments were conducted to investigate the role of map spatiality and icon mimeticism in facilitating text recall. A secondary goal was to explore an assumption of the conjoint retention hypothesis, that the visuospatial component of working memory is involved in retrieving map information. We manipulated display conditions to evaluate the separate and combined effects of map spatiality and icon mimeticism on text recall. We also utilized a concurrent task paradigm to assess both the recognition of spatial displays and the recall of map feature information. The results of all four experiments point to the mimeticism of icons as the key attribute of maps for facilitating recall, rather than the spatial layout of the map when visual displays and text are presented simultaneously during encoding. We also found no evidence indicating that maps are processed in a more spatial manner than are lists. Copyright 2000 Academic Press.

An Investigation of the Effects of Reciprocal Peer Tutoring on Achievement, Self-Efficacy, and Test Anxiety

Reciprocal peer tutoring (RPT) is a cooperative learning strategy which capitalizes on the benefit students receive from preparing to tutor one another. In these experiments we investigated the effects of RPT on the academic achievement, academic self-efficacy, and test anxiety of undergraduate students. Undergraduate education majors enrolled in either human growth and development or educational psychology participated in the study. Students developed a series of test questions, used these questions to quiz each other prior to unit examinations, and provided corrective feedback to the questions. Statistically significant findings were inconsistent across the experiments. In short, RPT appears to have, at best, inconsistent effects on achievement, test anxiety, and academic self-efficacy. Copyright 1998 Academic Press.

Effects of incarceration on HIV-infected individuals

Human immunodeficiency virus (HIV) infection is a critical problem among the incarcerated population, with rates as high as 17% being reported for prison systems in New York. The literature suggests that stressful living conditions and inherent defects in the immune system associated with HIV infection make prison populations more susceptible to a disproportionate decrease in their CD4 counts. To determine the effects of incarceration on HIV-infected individuals, the charts of 800 inmates were reviewed. Baseline (draw 1), 2- to 5-month (draw 2), and 6- to 12-month (draw 3) CD4 cell counts were obtained. Mean cell counts were calculated, and paired t-tests were used to identify differences. The group receiving antiretrovirals throughout showed no difference in mean CD4 cell count between draws 1 and 2 or between draws 1 and 3. The group not receiving HIV medications did not show a significant difference in CD4 cell counts between draws 1 and 2, but did show a significant difference between draws 1 and 3. For this group, the rate of decline in CD4 cells was greater than among an outpatient setting. The subsample of subjects initiating therapy prior to the second blood draw showed a significant increase in mean CD4 cell counts at draw 1 versus draw 2, but did not show a significant change when comparing draw 1 to draw 3. When examining subjects based on their antiviral status, the mean CD4 cell count at each of the draws was statistically associated with subjects' antiviral status. We conclude that incarceration causes a more rapid decrease in CD4 cells compared with an outpatient population, causing clinical significance on the normal course of HIV disease.

Affinity preparation of a protein inhibitor recognising a cell surface protease

Epithelial cell surfaces possess a trypsin-like protease, referred to as guanidinobenzoatase (GB). The cytoplasm of these cells contains an extractable protein (I) which recognises the cell surface GB by forming an enzyme-inhibitor complex (GB-I). Rhodamine-agmatine (Rh-Agm) was designed as a red fluorescent probe, directed to the active centre of GB, which can be used to locate cells with GB, employing fluorescence microscopy. Rh-Agm has a high affinity for GB and will displace I from GB-I on the surfaces of cells in frozen sections. Rh-Agm has been used to displace I from immobilised GB-I complexes on the surface of cultured colonic carcinoma cells in an affinity procedure aimed at purifying the inhibitors of GB obtained from cultured carcinoma cells. These inhibitors have been tested on protected frozen sections of normal colon and carcinoma of the colon, the formation of GB-I complexes being followed by a second yellow fluorescent probe which competes for the active centre of GB. The study of the protein-protein interactions to form GB-I has been facilitated by employing two synthetic fluorescent inhibitors of GB with differing affinities for GB and different fluorescent properties. The use of sections of tissue in this study has enabled a sequence of reactions to be carried out on the same cell surface GB, such that reversible inhibition reactions can be quickly demonstrated and recorded by fluorescence microscopy.

Further evidence for different isoenzymic forms of a cell surface protease, guanidinobenzoatase, associated with tumours

Normal colonic epithelial cells possess a cell surface protease referred to as guanidinobenzoatase (GB) and a corresponding cytoplasmic protein inhibitor of GB. Colonic carcinoma cells possess two isoenzymic forms of GB, the normal and the carcinoma specific form, each of which is recognised by the corresponding inhibitors present in the cytoplasm of colonic carcinoma cells. An affinity-purified inhibitor preparation obtained from the cytoplasm of cultured colonic carcinoma cells inhibited these two colonic carcinoma isoenzymic forms of GB but not the GB associated with other forms of tumour. The data suggest that each cell type possessing isoenzymic forms of cell surface GB also possesses the corresponding cell-specific inhibitors of GB.

GB (guanidinobenzoatase) cell surface protease and serum inhibitors in colorectal neoplasia

Cell surface proteases and their inhibitors are functionally related to the invasive properties and metastatic potential of tumour cells. Epithelial cells of the colorectal mucosa possess a cell surface protease referred to as guanidinobenzoatase (GB), which is similar, if not identical, to plasminogen activator. GB exists in isoenzymatic forms, one of which is associated with epithelial cells of normal colorectal mucosa and of adenomatous polyps, whilst another isoenzymatic form is associated with colorectal adenocarcinoma cells. Normal serum contains inhibitor proteins which recognize the isoenzymatic form of GB found on normal and adenomatous polyp epithelial cells but this inhibitor does not recognize the isoenzymatic form of GB associated with adenocarcinoma cells. The fluorescent probe 9-amino-acridine locates cells possessing active GB in frozen sections of colorectal mucosa. A technique is described which enables colorectal carcinoma cells to be highlighted by fluorescence microscopy whilst normal epithelial cells are distinguished by their lack of fluorescence. This is of biological and possibly diagnostic significance.

Observations on the conformational changes in the structure of a cell surface protease, followed by its ability to be recognised by competitive and non-competitive inhibitors

Lung tumour cells possess a cell surface protease which can be inhibited by a cytoplasmic protein inhibitor extracted from these cells. The dissociation of this enzyme-inhibitor complex on the surface of tumour cells in sections treated with 10(-4) M sodium dodecyl sulphate has been studied. The dissociation of the inhibitor and regain of enzymic activity was followed by the use of a fluorescent probe which binds to the active centre of the cell surface enzyme in a competitive manner.

Studies on the interaction and exchange of inhibitors and proteases on the surface of tumour cells in frozen sections

We have used frozen sections of squamous cell carcinoma as a convenient source of a cell surface protease associated with tumour cells. This protease has been referred to as guanidinobenzoatase (GB) and is now known to be functionally identical to tissue plasminogen activator (t-PA). The use of a fluorescent competitive inhibitor of GB enabled the enzymic status of GB to be determined, i.e. was the enzyme active, latent or removed from our test system. The cell surface GB was then demonstrated to interact with extractable cytoplasmic inhibitors obtained from these sections. We then used a protected form of the GB in the absence of these internal inhibitors; such sections were used to transfer the GB to fibrin fibrils, thus exposing the presumptive receptor on the tumour cell surfaces. Texas red labelled t-PA was then shown to bind to the tumour cells in these pretreated sections from which the GB had previously been removed. We believe that the surface of tumour cells can be used to study the interaction of the naturally occurring inhibitors with GB and also that the cell surface receptors for GB can be used to study the binding of t-PA to cell surfaces.

A simple fluorescent technique for the location of tumour cells in frozen sections of the head and neck region

Tumour cells possess cell surface proteases referred to as guanidinobenzoatase (GB) which are closely similar to plasminogen activator. Previous studies have demonstrated different isoenzymic forms of GB on tumour cells and normal cells which can be recognised by cytoplasmic protein inhibitors extracted from frozen sections of appropriate tissues. We now show that normal human serum possesses inhibitors which selectively recognise the isoenzymic forms of GB associated with normal cell surfaces but do not recognise the GB on tumour cell surfaces in frozen sections of tissue obtained from the head and neck regions.

Evidence for the functional similarity between tumour cell surface guanidinobenzoatase and tissue type plasminogen activator

Tumour cells possess a cell surface protease referred to as guanidinobenzoatase (GB). The active centre of GB binds the fluorescent probe 9-amino acridine (9-AA) and this binding enables cells possessing active GB to be located by fluorescent microscopy. GB binding of 9-AA was inhibited by prior treatment of sections of tumour tissue with a specific polyclonal antibody recognising the tumour associated protease tissue plasminogen activator (t-PA). GB binding of 9-AA was also inhibited by prior treatment of sections of tumour tissues with PAI-I, a protein inhibitor of plasminogen activatory. We conclude from these studies and kinetic analyses that GB and t-PA are very similar both in structure and function.

Evidence for distinct isoenzymic forms of a cell surface protease on normal colonic cells and on carcinoma cells from the same colon

Both normal and carcinoma cells of the colon possess the cell surface protease guanidinobenzoatase (GB). GB is similar to plasminogen activator. In fixed sections, the insolubilised GB can be located by the fluorescent probe 9-amino acridine (9-AA) which binds to the active centre of GB, causing cells possessing active GB to fluoresce yellow. Both cell types possess cytoplasmic proteins which can be extracted in isotonic saline and were shown to inhibit their respective cell surface GB. The formation of an enzyme-inhibitor complex was demonstrated by the failure of 9-AA to react with the cell surface GB inhibitor complex. The data presented indicate that the colonic carcinoma cells possess an isoenzymic form of GB not recognised by the inhibitors of GB extracted from normal colonic cells.

Temporary competitive inhibition of a tumour cell surface protease as a protective mechanism in the preparation of the membrane bound native enzyme in the presence of excess cytoplasmic inhibitors

Tumour cells possess a cell surface protease which is recognised and inhibited by a cytoplasmic protein extractable from frozen sections of tumour cells. In order to prepare sections with tumour cells carrying cell surface-bound native protease in the absence of this internal inhibitor we have used a reversible competitive inhibition step as a temporary measure to protect the active centre of GB whilst the cytoplasmic inhibitor is extracted from the frozen sections. These sections are described as protected in the sense that the enzyme is native and fully functional now that potential inhibitors have been extracted. The protected cell surface protease immobilised in the cell surface of squamous cell carcinoma cells has been used as the target for inhibition studies and displacement studies. The ability to follow these inhibition and exchange reactions concerning the cell surface protease has been made possible by virtue of the fluorescent probe, 9-amino acridine, which locates the active centre of the protease. Cells with active protease bind 9-amino acridine and fluoresce yellow; cells lacking this protease or having inhibited protease fail to bind 9-amino acridine and do not fluoresce.

Labelling of tumour cells with a biotinylated inhibitor of a cell surface protease

Our objective has been to prepare a biotinylated affinity probe for the active centre of a protease associated with the surface of tumour cells. We employed three model systems in which easily recognisable tumour cells containing the active protease were used as targets for the biotinylated affinity probe. These were: squamous cell carcinoma, leukaemia cells in muscle and outgrowths of prostate carcinoma cells grown in three dimensional collagen gels. The presence of the bound biotinylated affinity probe was demonstrated by its ability to bind Texas-red labelled streptavidin with the results that the tumour cells exhibited red fluorescence. This binding was shown to be competitive with 9-amino acridine, a compound known to bind to the active centre of the target protease. This technique depends upon the affinity of the active centre of an enzyme for a competitive inhibitor and therefore should be applicable to other enzyme systems employing suitable ligands for their active centres.

Evidence for cells possessing t-PA like activity in smears obtained from patients with oral squamous cell carcinoma

Squamous cell carcinoma cells possess a cell surface protease referred to as guanidinobenzoatase (GB) which is very similar to the single chain form of tissue type plasminogen activator. This enzyme binds fluorescent probes at its active center and cells possessing GB can be distinguished from those that lack this enzyme by fluorescent microscopic techniques. Normal squamous epithelial cells shed from the surface of the oral cavity lack GB and do not exhibit cell surface fluorescence when pretreated with such fluorescent probes. We have used this knowledge to design a simple technique for the rapid location of squamous cell carcinoma cells in oral smears; our results are presented in the form of colour prints in which the tumour cells can be easily distinguished from other cells by their fluorescence.

The targeting of agmatine-liganded mitomycin C to an enzyme on the surface of tumour cells

Tumour cells possess a cell surface protease referred to as guanidinobenzoatase (GB). We have synthesised a liganded form of mitomycin C which we refer to as MMC*. This MMC* has the fluorescent properties of mitomycin C and the additional ability to be directed to the active centre of GB by the agmatine moiety of the ligand. We have demonstrated the selective delivery of MMC* to the cell surface of tumour cells possessing active GB by fluorescent microscopy and competition experiments with molecules known to bind to the active centre of GB. The MMC* has a high affinity for tumour cell surface GB and we hope it may have potential in the selective delivery of mitomycin C in the chemotherapy of tumours in vivo.

Direct evidence for the cell surface location of a protease-inhibitor complex on intact leukaemia cells

The interaction of a protease with two fluorescent inhibitors has been studied using intact fixed leukaemia cells as the source of the membrane bound enzyme. Fresh rat leukaemia cells were disrupted and the cytosol collected; this extract was known to contain a protein inhibitor of guanidinobenzoatase (GB) associated with leukaemia cells. All the cytosolic proteins were derivatised with Texas red acid chloride. Leukaemia cells with latent GB failed to bind the Texas red inhibitor protein but did so after activation of GB. Competition experiments with 9-amino acridine (a fluorescent marker for the active site of GB) demonstrated that the Texas red-inhibitor protein could only bind to intact leukaemia cells when the active centre of GB was not already occupied by 9-amino acridine. This competition between these two fluorescent inhibitors demonstrated their specificity for GB. The use of intact leukaemia cells and the high molecular weight of the inhibitor protein precludes the possibility of any interaction between GB and inhibitor within the cells. It is concluded that GB and the GB-inhibitor complex of latent GB are located on the external surface of intact leukaemia cells.

A rapid technique for the fluorescent location of pleomorphic adenoma cells in frozen sections of human salivary glands

Both acinar cells and pleomorphic adenoma cells possess a cell surface protease, guanidinobenzoatase (GB) which can be located with a fluorescent probe for the active centre of this enzyme. We have developed a rapid, cheap, fluorescent technique for the differential location of pleomorphic adenoma cells and acinar cells in frozen sections of salivary glands. The fluorescence of other cells (which also possess GB) is selectively quenched, such that only the acinar and pleomorphic adenoma cells are visualised by fluorescent microscopy.

Competitive inhibition of a tumour cell surface protease. A rapid technique for in vitro testing of selective targeting systems

The active centre of a protease on the surface of tumour cells can be located by its affinity for an active site-directed inhibitor, 9-amino acridine. Cells which have uninhibited proteases, bind 9-amino acridine and fluoresce in resin sections. The leukaemic rat was used as a model system to provide tumour cells in a well defined location. Drugs when coupled to a ligand (directed to the active centre of the protease) compete for this binding site with 9-amino acridine. Thus, competitive inhibition of the tumour cell surface protease provides a rapid technique for demonstrating the delivery of liganded molecules to the surface of tumour cells in vitro.

Inhibition of trypsin-like enzymes on cells with rhodamine-aprotinin

Aprotinin, a polypeptide inhibitor of trypsin-like enzymes, has been labelled with rhodamine. Rhodamine-aprotinin inhibits trypsin in free solution in an identical manner to aprotinin. Rhodamine-aprotinin binds to trypsin-like enzymes on cells in formaldehyde fixed wax embedded sections. This technique has been used to locate cells possessing trypsin-like enzymes by means of fluorescent microscopy. In the present study we have used this technique to locate tumour cells.

Targeting adriamycin to tumour cells by means of an affinity ligand; a model system for drug delivery

Actively migrating tumour cells possess the proteolytic enzyme guanidinobenzoatase (GB) in an uninhibited form. This enzyme has been used as a target for the delivery of adriamycin to invasive tumour cells in frozen sections. An adriamycin-agmatine complex has been prepared which act as a competitive inhibitor of GB. Competition experiments have demonstrated that the adriamycin-agmatine complex competes with 9-aminoacridine for the active centre of GB associated with invasive tumour cells, located in the lymph nodes and in squamous cell carcinoma of the oral cavity. The technique described should be generally applicable to the targeting of drugs to cells.

A fluorescent study of ligands for guanidinobenzoatase, a protease associated with tumour cells

We have employed ethanol-fixed wax embedded sections of human breast tumours and smears of rat leukaemia cells to provide test systems with recognisable tumour cells amongst normal cells. We have used 9-aminoacridine to locate cells possesing guanidinobenzoatase, an enzyme which degrades fibronectin and which binds 9-aminoacridine to its active centre. The binding of 9-aminoacridine to tumour cells allows these cells to be located by fluorescent microscopy. Pre-treatment of these sections with BZAR, a known inhibitor of guanidinobenzoatase inhibited the binding of 9-aminoacridine to the tumour cells. These techniques defined the tumour cells in the sections; we then demonstrated by fluorescent microscopy that both Texas red-agmatine and BZAR also bound to the guanidinobenzoatase of these tumour cells. These fluorescent probes have been used as model compounds to illustrate the ability of both N-substituted agmatines and N-substituted arginines to deliver desired molecules to an enzyme on the surface of tumour cells. Replacement of these fluorescent moieties by cytotoxic moieties attached to the same ligands could lead to selective drug delivery to tumour cells.

Studies on the activity of a protease associated with cells at the advancing edge of human tumour masses in frozen sections

A fluorescent probe has been employed to study the status of a tumour associated protease, guanidinobenzoatase, in frozen sections of human tumours obtained from the head and neck regions. The results indicate that in vivo a naturally occurring inhibitor of guanidinobenzoatase effectively controls the activity of this enzyme on the majority of cells in a tumour mass. This inhibitor can be artificially displaced by formaldehyde treatment of the frozen sections and this treatment reveals the extent of latent enzyme in the section. In the frozen sections it was noticed that at the advancing edges of the tumour mass, the tumour cells possessed uninhibited guanidinobenzoatase, an enzyme known to degrade the link peptide between cells and fibronectin. It was shown that a synthetic inhibitor of guanidinobenzoatase selectively inhibited the guanidinobenzoatase of the tumour cells at the advancing edge of the tumour mass. It is suggested that the guanidinobenzoatase on cells at the leading edge of the tumour mass plays an important role in the invasion of adjacent host tissue. This synthetic inhibitor of guanidinobenzoatase has no inhibitory action on other trypsin-like enzymes and might therefore be of value in limiting the growth of the tumour mass in vivo.

The inhibition of a tumour cell surface protease in vivo and its re-activation by oxidation

Colonic tumour cells possess a cell surface protease capable of binding 9-aminoacridine to its active centre, thus locating cells when viewed under a fluorescence microscope. In vivo and in frozen sections, the enzyme is masked by a protein inhibitor. This inhibitor can be displaced by formaldehyde fixation of the tissue and then replaced by adding a fresh extract of colon or lung tissue. The inhibitor is modified by oxidation; provided by air, oxidized glutathione or potassium permanganate, resulting in a change in conformation in the inhibitor and this then results in the enzyme binding the fluorescent probe. The effect of oxidation can be reversed by dithiothreitol. It is proposed that these changes are brought about by a disulphide exchange acting on the inhibitor which indirectly controls the activity of the cell surface enzyme in vivo. The steps described above can be conveniently followed on sections of tissue mounted on a microscope slide; this has the advantage that the same cells can be monitored during a sequence of reactions. It is believed that these techniques could well be applied to other enzyme systems than the tumour protease described in this study.

Inhibition of guanidinobenzoatase by a substrate for trypsin-like enzymes

Guanidinobenzoatase is a proteolytic enzyme capable of degrading fibronectin and is a tumour associated enzyme. Guanidinobenzoatase has been shown to be an arginine selective protease and is distinct from trypsin, plasmin and thrombin, the latter enzymes can be assayed with bis(carbobenzyloxycarbonyl-L-argininamido)-Rhodamine or BZAR. Guanidinobenzoatase is inhibited by BZAR when the enzyme is assayed in free solution and when the enzyme is cell-bound in frozen sections of tumour containing tissues. It is proposed that BZAR and its analogues may be of value in inhibiting tumour cell invasion in vivo and also that the selectivity of BZAR may be used to direct cytotoxic drugs to tumour cells possessing active guanidinobenzoatase.

Inhibition of guanidinobenzoatase: evidence for multiple forms of this protease on different tumour cells

Guanidinobenzoatase is a proteolytic enzyme capable of degrading fibronectin and is a tumour associated enzyme. 9-Aminoacridine is a competitive inhibitor of this enzyme and has been used to locate cells possessing this enzyme in wax embedded sections by means of fluorescent microscopy. Naturally occurring inhibitors of guanidinobenzoatase can be extracted from different tissues. These inhibitors show selectivity in their ability to inhibit the binding of 9-aminoacridine to different types of tumour cells which have invaded human liver tissue. Inhibition is non-competitive and reversible. The results indicate that guanidinobenzoatase exists in a number of different forms on the surface of different tumour cells. These different forms of the enzyme were recognised by inhibitors obtained from different organs. It is suggested that these inhibitors may have a regulatory role in tumour cell migration.

Fluorescent inhibitors of a cell surface protease used to locate leukaemia cells in kidney sections

Guanidinobenzoatase is a trypsin-like protease on the surface of cells capable of migration, for example leukaemia cells. We have used a number of fluorescent probes that are competitive inhibitors of guanidinobenzoatase to locate leukaemia cells in resin sections of kidney tissue obtained from leukaemic rats. We have demonstrated how this competitive inhibition system can be used to direct desired molecules (such as cytotoxic drugs) to these cells and to monitor the arrival of such compounds at the active site of guanidinobenzoatase. The principles developed in this study could equally well be applied to other enzymes on other cells provided suitable competitive inhibitors were designed. The presence of an enzyme on the surface of a cell can be used to direct molecules to that cell provided that these molecules contain a functional group that acts as an inhibitor for the chosen enzyme.

The role of inhibitors in the fluorescent staining of benign naevus and malignant melanoma cells with 9-amino acridine and acridine orange

Guanidinobenzoatase is a trypsin-like protease capable of degrading fibronectin. An inactive form of guanidinobenzoatase is present on the surface of benign naevus cells and these cells stain very weakly with 9-aminoacridine, a known competitive inhibitor of guanidinobenzoatase. Malignant melanoma and metastatic malignant melanoma cells exhibit strong surface staining with 9-aminoacridine and also exhibit strong staining of cytoplasmic RNA with acridine orange. These simple fluorescent techniques have been used to distinguish benign naevus cells from malignant melanoma cells in human skin sections. This difference in cell surface staining with 9-aminoacridine has been demonstrated to be caused by the presence or absence of an inhibitor. The inhibitor can be displaced from the cell surface enzyme and then replaced by an affinity purified inhibitor obtained from fresh liver homogenates. It is proposed that the inhibition or control of cell surface guanidinobenzoatase may be one of the regulatory mechanisms by which benign naevus cells are prevented from developing into malignant melanoma cells.

Further inhibition studies on guanidinobenzoatase, a trypsin-like enzyme associated with tumour cells

Guanidinobenzoatase is a proteolytic enzyme capable of degrading fibronectin and is a tumour associated enzyme. Guanidinobenzoatase has been shown to be an arginine selective protease and is distinct from trypsin, plasminogen activator, plasmin, thrombin and a newly described tumour associated enzyme specific for guanidino phenylalanine residues. These conclusions have been derived from inhibition studies employing 4-methyl-p-guanidinobenzoate as substrate. Three active site titrants for trypsin have been shown to be good substrates for guanidinobenzoatase. A new active site titrant for trypsin, rhodamine bisguanidinobenzoate, can also be used to assay guanidinobenzoatase in a stoichiometric manner. This active site titrant can be employed to label guanidinobenzoate on the surface of leukaemia cells.

Design of fluorescent probes for an enzyme on the surface of tumour cells

The proteolytic enzyme guanidinobenzoatase is specific for arginyl peptide bonds and is capable of degrading fibronectin. This enzyme is associated with the cell surface of tumour cells in formaldehyde-fixed wax-embedded sections of human pathological tissue. We have designed fluorescent probes for the active site of guanidinobenzoatase: these probes act as competitive inhibitors and can be used to locate cells possessing guanidinobenzoatase. The processes of designing probes, testing their potential as inhibitors, and applying these probes to tumour cell location, all depend upon affinity principles.

Evidence for inhibitors of the cell surface protease guanidinobenzoatase

Guanidinobenzoatase is a protease present on the surface of tumour cells. The present study describes the isolation of a protein inhibitor of guanidinobenzoatase obtained from extracts of liver and pancreas and purified by affinity techniques. Pancreatic acinar cells have been shown to possess a latent form of guanidinobenzoatase and this latency is due to complex formation with the inhibitor. A fluorescent marker has been employed to demonstrate the presence or absence of the inhibitor on sections of pancreatic tissue. The inhibitor has been shown to be exchangeable with liver and pancreatic inhibitors obtained from different species. It is postulated that these inhibitors may play a role in enzyme control.

The design of fluorescent probes which bind to the active centre of guanidinobenzoatase. Application to the location of cells possessing this enzyme

Cells possessing a known enzymic activity may be located by fluorescent probes designed to act as competitive inhibitors of this enzyme. We have prepared a series of dansyl N-substituted guanidino derivatives which bind to the active centre of guanidinobenzoatase. 9-Aminoacridine also acts as a competitive inhibitor and behaves similarly to these guanidino derivatives. These fluorescent probes have been used to locate tumour cells possessing this enzyme in thin sections of fixed tissue by employing fluorescent microscopy.

Evidence for metal inhibition of tumour membrane-bound neutral protease and the control of tumour-induced target cell cytolysis

Previous studies have characterized the enzymatic properties and inhibition of a trypsin-like neutral protease on the surface of Ehrlich ascites cells by means of kinetic analysis. The present study links these kinetic studies with the recently reported role of a tumour-cell membrane-bound serine protease in tumour-induced target cell lysis. Low-mol.-wt inhibitors of this cell-surface trypsin-like neutral protease exhibited a corresponding ability to prevent tumour-induced haemolysis. High-mol.-wt inhibitors of trypsin in free solution had no inhibitory action either on the tumour-bound enzyme or on the ability of tumour cells to lyse erythrocytes. Fragments of tumour-cell membrane retain both the trypsin-like neutral protease activity and the ability for haemolysis. This study represents a correlation between an easily assayed membrane-bound enzyme on tumour cells and a function of possible biological relevance.

Evidence for carriage of silver by sulphadimidine: haemolysis of human erythrocytes

1 Human erythrocytes suspended in isotonic saline haemolyse in the presence of both Ag+ ions and sulphadimidine. 2 Neither Ag+ ions nor sulphadimidine on their own will haemolyse erythrocytes suspended in isotonic saline. 3 At constant Ag+ ion concentration the degree of haemolysis of saline-suspended erythrocytes depends upon the concentration of sulphadimidine. 4 Human erythrocytes suspended in isotonic sucrose (chloride-free) haemolyse in the presence of Ag+ ions. 5 Sulphadimidine in chloride-free sucrose competes with erythrocytes for Ag+ ions resulting in stoichiometric protection of the erythrocytes from the haemolytic action of Ag+ ions. 6 Haemolysis occurs when each erythrocyte receives approximately 1.2 X 10(9) Ag+ ions whether suspended in saline or sucrose. 7 Sulphadimidine acts as a carrier for Ag+ ions and so prevents their precipitation as AgCl when erythrocytes are suspended in saline.

Evidence for the carriage of silver by sulphadimidine: inhibition of proteolytic enzymes

1 Trypsin in free solution and trypsin-sepharose were shown to be inhibited by Ag+ in the absence of Cl-. 2 In the presence of Cl- and absence of a suitable carrier, Ag+ has no inhibitory action on trypsin or chymotrypsin. 3 Sulphadimidine bound Ag+ in the presence of Cl-, and carried the Ag+ to both trypsin and chymotrypsin in free solution as well as to trypsin-sepharose leading to the inhibition of all these enzyme systems. 4 The neutral protease of tumour cell surfaces was inhibited by Ag+ transported by sulphadimidine in the presence of Cl-. 5 Kinetic data demonstrated the requirements for both Ag+ and carrier to effect inhibition, the degree of inhibition being directly related to the molarity of each of these reagents. 6 The known inhibition of trypsin by Ag+ binding to histidine in the active site has been defined in mechanistic terms employing the sulphonamide drug, sulphadimidine, to illustrate this exchange mechanism.

Inhibition of free and bound trypsin-like enzymes

1. The inhibition of beta-naphthylamidase activity of free trypsin, trypsin-Sepharose and a trypsin-like neutral protease on the surface of tumour cells have been studied in independent systems and with mixtures of free trypsin plus surface-bound trypsin. 2. Kinetic data have demonstrated that high-molecular-weight (protein) inhibitors of free trypsin are less effective inhibitors of trypsin-Sepharose and fail to inhibit the cell surface neutral protease. 3. Inhibition of mixtures of free trypsin plus trypsin-Sepharose follows independent kinetic plots for each component. The free trypsin is reacted before any Sepharose-bound trypsin reacts with high-molecular-weight inhibitors. 4. Low-molecular-weight inhibitors of trypsin also inhibit bound trypsin equally well. 5. Papain-derived peptides from high-molecular-weight inhibitors of trypsin inhibit free trypsin, trypsin-Sepharose and the cell-surface neutral protease almost equally well. 6. Fluorescence microscopy has shown that a high-molecular-weight inhibitor of trypsin does not bind to the tumour cell-surface neutral protease, but it does bind to trypsin-Sepharose. 7. The cell-surface neutral protease has been shown to be capable of activation of latent beta-naphthylamidase activity in the presence of excess extracellular inhibitors of free trypsin. 8. The mechanism by which trypsin-Sepharose remains partially active in the presence of excess inhibitor necessary to inhibit an equivalent quantity of free trypsin has been discussed. 9. These studies indicate that a search for inhibitors which are selectively active against the cell-surface neutral protease and have no action on trypsin-like enzymes in free solution must take into account the modifying effects of the cell surface on neutral protease activity.

Inhibition of human and bovine sperm acrosin by divalent metal ions. Possible role of zinc as a regulator of acrosin activity

Human and bovine spermatozoa have been collected and washed repeatedly with isotonic saline to remove seminal plasma inhibitors and activate the acrosin. Then the acrosin activity of the cells was assayed with alpha-N-Benzoyl-DL-Arg-beta-naphthylamide (BANA). It was found that the surface-bound enzyme was not inhibited by high molecular weight inhibitors of trypsin but was markedly inhibited by low molecular weight trypsin inhibitors. Divalent metals (Zn++, Cu++, Hg++, Co++, Cd++) were all efficient inhibitors of acrosin on the washed cells. It was shown that the removal of zinc or copper from acrosin completely restored activity. It is proposed that the different levels of zinc in the male and female genital tract regulate acrosin activity. Aged cells released a soluble acrosin which was inhibited by serum and seminal plasma inhibitors of trypsin-like enzymes as well as by zinc ions in an identical manner to the surface-bound enzyme.

Interaction of alpha, beta-diethyl stilbestrol 4,4'-bisphosphate with arginyl substrates resulting in apparent inhibition of trypsin and thrombin

1. alpha, beta-Diethyl stilbestrol 4,4'-bisphosphate (up to 7.0 mM) had no inhibitory action on trypsin assayed with the lysyl substrate, L-lysine nitroanilide dihydrobromide or by active-site titration with 4-methyl umbelliferyl-p-guanidinobenzoate X HCl. 2. Diethyl stilbestrol bisphosphate had an inhibitory action on the tryptic cleavage of arginyl peptides when fluorescein-labelled soluble casein was used as a substrate. 3. This inhibitory action was caused by complex formation between diethyl stilbestrol bisphosphate and susceptible arginyl residues in the substrate, inhibition being reversed by increasing the substrate concentration or adding competitive arginine molecules. 4. This type of inhibition involving substrate modification is referred to as 'apparent inhibition' of trypsin and was confined to arginyl peptide bond cleavage. 5. Thrombin specifically cleaves arginyl bonds in fibrinogen to initiate clot formation by the production of fibrin monomers. Diethyl stilbestrol bisphosphate was shown to cause apparent inhibition of clot formation in whole plasma and fibrinogen solutions in the presence of added thrombin. 6. Kinetic data of clot formation demonstrated a threshold level of diethyl stilbestrol bisphosphate (approximately 5 mM) necessary to be exceeded before these apparent inhibitory effects were observed. 7. The mechanism of 'apparent inhibition' is briefly discussed in relation to the more usual inhibition of an enzyme activity due to the direct action of an inhibitor with the enzyme under study.

Inhibition of trypsin and papain by sodium aurothiomalate mediated by exchange reactions

Sodium aurothiomalate has been shown to participate in exchange reactions leading to the inhibition of trypsin; for this exchange to take place it was necessary to include in the test system a suitable thiol, such as N-acetyl-cysteine. Neither N-acetyl-cysteine nor aurothiomalate on their own had any inhibitory action on trypsin. The results indicate that aurothiomalate dissociates in the presence of a carrier to form thiosuccinate and gold. The gold is responsible for trypsin inhibition since independent experiments demonstrated that the total concentration of thiosuccinate was insufficient to cause the observed inhibition of trypsin. Bovine serum albumin was shown to act as a carrier in place of N-acetyl-cysteine. It is known that histidine in the active centre of trypsin binds heavy metal ions with consequent inhibition of the enzyme. In this study, imidazole was shown to act as a carrier for gold from aurothiomalate to trypsin resulting in inhibition. This inhibition by gold was reversed when higher concentrations of imidazole were added to the test system due to competition for the trypsin-bound gold by imidazole. Conversely, the thiol enzyme papain was re-activated in the presence of low concentrations of sodium aurothiomalate and inhibited by higher concentrations of this reagent in a biphasic manner. This observation will be discussed in relation to the dissociation of sodium aurothiomalate. These observations can also be explained in terms of exchange reactions involving thiols and free metal ions.

Inhibition of thrombin cleavage of fibrinogen by polyestradiol phosphate; interaction with the crucial arginine residues in fibrinogen required for enzymic cleavage

1. Polyestradiol phosphate (PEP) has been demonstrated to have inhibitory activity against hyaluronidase, acid phosphatase and alkaline phosphatase (Fernö et al., 1958). 2. PEP has a marked inhibitory action against thrombin in the blood clotting reaction in which thrombin cleaves four fibrinopeptides from fibrinogen resulting first in the formation of monomeric fibrin and then polymeric fibrin fibrils (Baughman, 1970; Magnusson, 1970).