Trimester-specific diagnostic accuracy of ultrasound for detection of placenta accreta spectrum: systematic review and meta-analysis

BACKGROUND

This study aimed to assess the diagnostic accuracy of ultrasound for detecting placenta accreta spectrum (PAS) during the first trimester of pregnancy and compare it with the accuracy of second and third trimester ultrasound in pregnancies at risk for PAS.

METHODS

PubMed, Embase, and Web of Science, databases were searched to identify relevant studies published from inception until March 10th, 2023. Inclusion criteria were all studies, including cohort, case-control, or cross-sectional studies, that evaluated the diagnostic accuracy of first trimester ultrasound performed prior to 14 weeks (first trimester) or after 14 weeks of gestation (second/third trimester) for diagnosis of PAS in pregnancies with clinical risk factors. The primary outcome was to assess the diagnostic accuracy of ultrasound in detecting PAS in the first trimester, and to compare it with the accuracy of ultrasound in the second and third trimesters. The secondary outcome was to evaluate the diagnostic accuracy of each ultrasonographic marker individually across the trimesters of pregnancy. Reference standard was PAS confirmed at pathological or surgical examination. The potential of ultrasound and different ultrasound signs to detect PAS was assessed by computing summary estimates of sensitivity, specificity, diagnostic odds ratio (DOR) and positive (LR+) and negative (LR-) likelihood ratios.

RESULTS

A total of 37 studies including 5,764 pregnancies at risk of PAS, with 1,348 cases of confirmed PAS, were included in our analysis. The meta-analysis yielded a sensitivity of 86% (95% CI: 78%, 92%) and specificity of 63% (95% CI: 55%, 70%) during the 1st trimester, while the sensitivity was 88% (95% CI: 84%, 91%) and specificity was 92% (95% CI: 85%, 96%) during the 2nd/3rd trimester. Regarding ultrasonographic markers examined in the 1st trimester, lower uterine hypervascularity exhibited the highest sensitivity of 97% (95% CI: 19%, 100%), and uterovesical interface irregularity demonstrated the highest specificity of 99% (95% CI: 96%, 100%). However, in the 2nd/3rd trimester, loss of clear zone had the highest sensitivity of 80% (95% CI: 72%, 86%), while uterovesical interface irregularity exhibited the highest specificity of 99% (95% CI: 97%, 100%).

CONCLUSION

First trimester ultrasound has similar accuracy to second and third trimester ultrasound for the diagnosis of PAS. Routine first trimester ultrasound screening for patients at high risk of PAS may improve detection rates and allow earlier referral to tertiary care centers for pregnancy management. This article is protected by copyright. All rights reserved.

Mosunetuzumab in combination with CHOP in previously untreated DLBCL: safety and efficacy results from a phase 2 study

Up to 40% of patients with diffuse large B-cell lymphoma (DLBCL) are refractory to or relapse after first-line therapy, highlighting the need for better treatments. Mosunetuzumab is a CD20 × CD3 bispecific antibody that engages and redirects T cells to eliminate malignant B cells. In this phase 2, open-label study (NCT03677141), 40 patients (52.5% with international prognostic index ≥3) with previously untreated DLBCL initiated 6 cycles of IV mosunetuzumab with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy. Mosunetuzumab was administered in cycle 1 as step-up doses to mitigate cytokine release syndrome [CRS], and a dose of 30 mg was given on day 1 of cycles 2-6. Efficacy end points included objective and complete response rates, as determined by the investigator, via positron emission tomography-computed tomography, using Lugano 2014 criteria (87.5% and 85.0%, respectively). At a median follow-up of 32.0 months, the estimated 2-year progression-free survival and event-free survival rates were 65.4% (95% confidence interval [CI], 49.5-81.4) and 60.4% (95% CI, 44.7-76.1), respectively. CRS occurred in 60.0% of patients; all events were grade 1 (45.0%) or grade 2 (15.0%) and occurred primarily in cycle 1. Mosunetuzumab-related grade ≥3 neurologic adverse events (AEs) potentially consistent with immune effector cell-associated neurotoxicity syndrome occurred in 1 patient (2.5%). Grade 5 AEs were reported in 2 patients. Neutropenia occurred in 70.0% of patients, mostly during cycle 1 and was of short duration. These findings demonstrate promising activity and a manageable safety profile for mosunetuzumab-CHOP and warrant further investigation of mosunetuzumab in first-line combination regimens for DLBCL.

Brexucabtagene Autoleucel for Relapsed or Refractory Mantle Cell Lymphoma in Standard-of-Care Practice: Results From the US Lymphoma CAR T Consortium

PURPOSE

Brexucabtagene autoleucel (brexu-cel) is an autologous CD19-directed chimeric antigen receptor (CAR) T-cell therapy approved for relapsed/refractory mantle cell lymphoma (MCL). This therapy was approved on the basis of the single-arm phase II ZUMA-2 trial, which showed best overall and complete response rates of 91% and 68%, respectively. We report clinical outcomes with brexu-cel in the standard-of-care setting for the approved indication.

PATIENTS AND METHODS

Patients who underwent leukapheresis between August 1, 2020 and December 31, 2021, at 16 US institutions, with an intent to manufacture commercial brexu-cel for relapsed/refractory MCL, were included. Patient data were collected for analyses of responses, outcomes, and toxicities as per standard guidelines.

RESULTS

Of 189 patients who underwent leukapheresis, 168 (89%) received brexu-cel infusion. Of leukapheresed patients, 79% would not have met ZUMA-2 eligibility criteria. Best overall and complete response rates were 90% and 82%, respectively. At a median follow-up of 14.3 months after infusion, the estimates for 6- and 12-month progression-free survival (PFS) were 69% (95% CI, 61 to 75) and 59% (95% CI, 51 to 66), respectively. The nonrelapse mortality was 9.1% at 1 year, primarily because of infections. Grade 3 or higher cytokine release syndrome and neurotoxicity occurred in 8% and 32%, respectively. In univariable analysis, high-risk simplified MCL international prognostic index, high Ki-67, TP53 aberration, complex karyotype, and blastoid/pleomorphic variant were associated with shorter PFS after brexu-cel infusion. Patients with recent bendamustine exposure (within 24 months before leukapheresis) had shorter PFS and overall survival after leukapheresis in intention-to-treat univariable analysis.

CONCLUSION

In the standard-of-care setting, the efficacy and toxicity of brexu-cel were consistent with those reported in the ZUMA-2 trial. Tumor-intrinsic features of MCL, and possibly recent bendamustine exposure, may be associated with inferior efficacy outcomes.

Clinical advances in epigenetic therapies for lymphoma

BACKGROUND

Advances in understanding of cancer biology, genomics, epigenomics, and immunology have resulted in development of several therapeutic options that expand cancer care beyond traditional chemotherapy or radiotherapy, including individualized treatment strategies, novel treatments based on monotherapies or combination therapy to reduce toxicities, and implementation of strategies for overcoming resistance to anticancer therapy.

RESULTS

This review covers the latest applications of epigenetic therapies for treatment of B cell, T cell, and Hodgkin lymphomas, highlighting key clinical trial results with monotherapies and combination therapies from the main classes of epigenetic therapies, including inhibitors of DNA methyltransferases, protein arginine methyltransferases, enhancer of zeste homolog 2, histone deacetylases, and the bromodomain and extraterminal domain.

CONCLUSION

Epigenetic therapies are emerging as an attractive add-on to traditional chemotherapy and immunotherapy regimens. New classes of epigenetic therapies promise low toxicity and may work synergistically with other cancer treatments to overcome drug resistance mechanisms.

BTK Inhibitors and CAR T-Cell Therapy in Treating Mantle Cell Lymphoma-Finding a Dancing Partner

PURPOSE OF REVIEW

This review focuses on the feasibility of combining Bruton's tyrosine kinase (BTK) inhibitors (BTKis) with chimeric antigen receptor (CAR) T-cell therapy in patients with relapsed or refractory (R/R) mantle cell lymphoma (MCL). Potential scenarios for combination treatment with these agents are presented.

RECENT FINDINGS

BTKis and CAR T-cell therapy have revolutionized the treatment paradigm for R/R MCL. Ibrutinib, acalabrutinib, and zanubrutinib are covalent irreversible BTKis approved for R/R MCL. Brexucabtagene autoleucel was the first CAR T-cell therapy approved for R/R MCL based on findings from the ZUMA-2 trial. There is evidence to suggest that combination treatment with BTKis and CAR T-cell therapy may improve CAR T-cell efficacy. As BTKis and CAR T-cell therapy become mainstays in R/R MCL therapy, combination treatment strategies should be evaluated for their potential benefit in R/R MCL.

Fetal myelomeningocele diagnosed in the antenatal period: Maternal-fetal characteristics and their relationship with pregnancy decision-making

BACKGROUND

Spina bifida is the most common fetal anomaly of the central nervous system, which affects approximately 1:1000 live births in the United States. Myelomeningocele (MMC) is the most common presentation of spina bifida, representing half of these cases. Given the deformation to the spinal cord and the nerve roots, this defect may result in significant morbidity to infants and major life-long disabilities. In this study we aimed to identify maternal and fetal characteristics associated with expectant management or termination of pregnancy in the setting of antenatally diagnosed MMC. We hypothesized that the level of the defect would correlate with patient's decision to continue the pregnancy.

METHODS

A retrospective cohort analysis was performed with patients who had presented to the Cleveland Clinic Fetal Care Center between 2005-2017.

RESULTS

Our data showed 36% of patients with antenatal diagnosis of MMC elected for second trimester terminations versus 64% who chose to continue their pregnancy and deliver either by cesarean section or vaginal delivery. Based on ultrasound findings, there were no significant differences between these two groups. Maternal body mass index was significantly higher in those who continued pregnancies (p = 0.036). In addition, the fetal diagnostic methods chosen by patients were significantly different. Those who elected to terminate were more likely to pursue amniocentesis (p = 0.03) and less likely to opt for MRI characterization of the fetus (p = 0.007).

CONCLUSION

We conclude, in the setting of fetal MMC diagnosed during pregnancy, patients often rely less on the associated ultrasonographic findings. Personal decisions likely influence the choice of other fetal diagnostic modalities. Other than BMI, we did not see an association between maternal factors and decisions regarding second trimester pregnancy termination.

Epidemiology and control of vancomycin-resistant enterococci in a regional neonatal intensive care unit

BACKGROUND

After the occurrence of two cases of bloodstream infection with vancomycin-resistant enterococci (VRE) in our regional neonatal intensive care unit, we studied the epidemiology of VRE and applied extensive infection control measures to the unit to control VRE transmission.

METHODS

Infection control measures applied to the unit included weekly surveillance for VRE colonization; education; cohorting of VRE-positive, VRE-negative and VRE-exposed babies with separate personnel and equipment for each group; use of gowns and gloves on room entry; and hand washing before and after each patient contact. Risk factors for VRE colonization were determined with a stepwise logistic regression model.

RESULTS

Thirty-three (40.2%) babies became colonized with VRE. The VRE colonization rate was reduced from 67% to 7% after implementation of infection control measures. Prolonged antimicrobial treatment and low birth weight were significantly associated with an increased risk of VRE colonization.

CONCLUSION

VRE can spread rapidly among newborns in a regional neonatal intensive care unit. Strict infection control measures can reduce the rate of VRE colonization among neonates.

Systemic hyperoxia decreases vascular endothelial growth factor gene expression in ischemic primate retina

OBJECTIVES

To determine whether systemic hyperoxia can reverse retinal hypoxia and decrease vascular endothelial growth factor (VEGF) gene expression in ischemic nonhuman primate retina.

METHODS

Six eyes of 3 cynomolgus monkeys were studied. Retinal ischemia was induced via laser vein occlusion and confirmed with fluorescein angiography. Animals were randomly assigned to treatment with either 21% or 100% inhaled oxygen. Arterial PO2 was monitored while systemic acid-base status was maintained. An oxygen microelectrode on a micromanipulator was used to measure preretinal oxygen concentrations in ischemic and nonischemic retina in situ. RNA was isolated from fresh whole retinas, and VEGF messenger RNA levels were quantified with Northern blotting.

RESULTS

The preretinal PO2 in ischemic retina was less than the PO2 in nonischemic retina in animals breathing 21% oxygen (intervascular zone PO2, 14.3+/-0.53 vs 21.8+/-0.55 mm Hg; P=.002). After 8 hours of systemic hyperoxia (arterial PO2, 512+/-18 mm Hg), the preretinal PO2 in ischemic retina increased to 166.2+/-15.6 mm Hg (21.8% oxygen) and retinal VEGF messenger RNA levels were reduced by an average of 55%.

CONCLUSIONS

These data demonstrate that systemic hyperoxia can lower retinal VEGF gene expression and reoxygenate ischemic adult primate retina.

Continuous measurements of intra-vascular pO2 in the pig optic nerve head

BACKGROUND

The measurement of oxygen concentration in the microvasculature of a tissue is important for the understanding of oxygen delivery.

MATERIAL AND METHODS

A technique was developed to measure in a continuous manner the partial pressure of oxygen (pO2) in the optic nerve microvasculature of the minipig. This technique is based on the quenching by oxygen of the phosphorescence emitted by a dye that is injected intravenously. It provides measurements of the intra-vascular pO2 and was applied simultaneously with measurements of the extra-vascular pO2 with microelectrodes and blood flow by laser Doppler flowmetry.

RESULTS

We demonstrate for the first that the optic nerve head intra-vascular pO2 increases during dark adaptation. Furthermore no change in extra-vascular pO2 and blood flow could be detected.

CONCLUSIONS

Based on Krogh's model, these results suggest that oxygen consumption by the optic nerve head tissue increases during dark adaptation.

[Early alterations in release of nitrogen monoxide by the retinal after experimental venous occlusion]

PURPOSE

We present hereby some results indicating that there is a significant decrease in the release of NO by the retina immediately after branch-venous occlusion (BVO).

METHODS

Using an NO microprobe we measured (NO) in the preretinal vitreous of miniature pigs before and two hours aRer bvo. Conventional and electronic microscopy were performed on the affected retina.

RESULTS

At the retinal surface (NO) was reduced to 25% of the previous value two hours after BVO, at the same time significative oedema of the inner retina was observed.

CONCLUSIONS

Immediately after BVO there is a significative decrease in the amount of NO released by the affected retina, parallel to the first evidences of an oedema of the inner retinal layers.

Cocaine-stimulated endothelin-1 release is decreased by angiotensin-converting enzyme inhibitors in cultured endothelial cells

OBJECTIVE

The primary aim was to determine the action of pathophysiologically relevant cocaine concentrations (10(-7)-10(-5) M) on endothelin-1 (ET-1) release from cultured endothelial cells under various cellular conditions. Further aims were to evaluate the effect of angiotensin-converting enzyme inhibitors on cocaine-treated endothelial cells, to assess their potential for inhibition of ET-1-stimulated release.

METHODS

Endothelin-1 release into the media was evaluated by radioimmunoassay under basal conditions and after 24 h treatment of endothelial cells with cocaine hydrochloride (HCl), or cocaine HCl and ACE inhibitors, captopril and lisinopril. The effect of serum and plasma under these conditions was also investigated.

RESULTS

Cocaine HCl stimulated ET-1 release in a dose response fashion that was independent of plasma or serum factors. Furthermore, cocaine-stimulated ET-1 release was inhibited by administration of angiotensin-converting enzyme inhibitors captopril and lisinopril.

CONCLUSIONS

These findings suggest that cocaine can directly stimulate endothelial cells to release ET-1 and that the observed increase is independent of serum or plasma factors. Furthermore, cocaine-stimulated endothelin-1 release appears to be mediated at least in part by the angiotensin system. These observations provide a framework for understanding the cellular mechanisms involved in cocaine-induced vasoconstriction.

Nitric oxide controls arteriolar tone in the retina of the miniature pig

PURPOSE

Experimental evidence indicates that the retinal microcirculation is mainly controlled by factors released from the tissue surrounding the arterioles. This study explores whether nitric oxide (NO), a possible factor, is released in the retina and controls the arteriolar tone.

METHODS

Using a NO microprobe, the authors measured [NO] in the preretinal vitreous of miniature pigs as a function of distance from the retinal surface. Additionally, the NO-synthase inhibitor nitro-L-arginine was pressure injected. Finally, the retinal pool size of arginine and its biosynthesis from 14C(U)-glucose were biochemically assessed on retinal tissue and acutely isolated Müller cells.

RESULTS

At the retinal surface, [NO] measured 6 to 9 microM, and, in the vitreous, it fell to zero approximately 180 microns away from the retina. Therefore, NO is degraded faster in the vitreous (65 to 80 microM.minute-1) than in aqueous solution. Light flicker stimulation of the dark-adapted retina induced a reversible increase of [NO] (approximately 1.6 microM). Preretinal juxta-arteriolar microinjections of nitro-L-arginine (0.6 mM) induced a segmental and reversible arteriolar vasoconstriction of 45%; in contrast, intravenous infusion of nitro-L-arginine had no measurable effect on arteriolar diameter. The retinal pool size of arginine was small (< or = 200 microM), but there was an important rate of arginine biosynthesis in Müller cells.

CONCLUSIONS

These results strongly suggest that cells in the retina, other than endothelial cells, produce and release NO, which in turn controls the basal dilating arteriolar tone in the inner retina.

[Constitutional release of nitrogen monoxide (NO) by the retina of the minipig is a major determinant of arteriolar basic tonus in the internal retina]

PURPOSE

NO is a nonpolar gas, which diffuses across cell membranes in an isotropic fashion. In relatively large arteries NO has been identified as the endothelium-derived releasing factor and the current hypothesis is that NO controls the vascular tone. We are investigating an alternative hypothesis proposing that the retinal tissues surrounding the arterioles contribute in the process of NO production.

METHODS

We performed flicker light stimulation in anesthetized minipigs (hypnodyl 100 mg/hr, tubocurarine 0.1 mg/hr und N2O) in steady-state of normoxia-normocapnia. An NO-microprobe mounted on a micromanipulator was introduced into the eye through the pars plana and positioned on the preretinal space in a zone free of visible vessels. Preretinal NO gradient and recording of NO release variations in response to flicker light stimulation were performed so as periarteriolar microinjections of nitro-L-arginine.

RESULTS

When advancing the NO-probe from the vitreous towards the retina we recorded an NO-gradient corresponding to an efflux of 7.1 pMol x min-1 x cm-2 (N = 9). With the microprobe positioned close to the retina and after 60 min dark adaptation we recorded a mean increase in NO release of 1.59 muMol +/- 0.13 SE. After periarteriolar microinjection of nitro-Larginine we recorded a transitory reversible vasoconstriction.

CONCLUSIONS

These results indicate that a process occurring in the extravascular tissue of the retina modulates the production of NO and that constitutional NO release by the retina is a major determinant of the basal retinal arteriolar tone.

[The role of nitric oxide in retinal vasomotor regulation]

Nitric oxide (NO) is one of the most important messenger molecules dilating blood vessels in response to neurotransmitters and serving itself as a neurotransmitter in the brain. We explored its role in the retinal vascular regulation using a sensitive and specific NO microsensor and local perivascular microinjections of NO-synthase inhibitor (nitro-L-arginine in the intact eye of anesthetized miniature pigs. Our findings suggest that NO release is involved in the regulation of basal vascular tone in the inner retina. In contrast hypercapnia and hypoxia induce vasodilatation in an NO independent mechanism.

Microinjection of L-lactate in the preretinal vitreous induces segmental vasodilation in the inner retina of miniature pigs

PURPOSE

The authors investigated the hypothesis that the retinal vasomotor effect of acute hypoxia is mediated by lactate.

METHODS

Retinal vasomotor arteriolar response was measured in the intact eyes of miniature pigs after systemic administration and after local preretinal juxta-arteriolar microinjection of lactate.

RESULTS

Injection of L-lactate (physiologically produced lactate) into the systemic circulation decreased the arterial blood pH but did not dilate the retinal arterioles. By contrast, microinjections of L-lactate (0.5 mol/l, pH 2) into the juxta-arteriolar vitreous induced a reversible segmental vasodilation of 32 +/- 4% (standard deviation). This vasodilation did not depend on periarteriolar pH lowering because microinjections of a 0.5 mol/l L-lactate at neutral pH also dilated segmentally the retinal arterioles (37 +/- 5.5%). The effect of lactate was stereospecific because microinjections of the isomer D-lactate (0.5 mol/l, pH 2) did not affect the arteriolar caliber (P = 0.63). Perfusion of the eye with the cyclo-oxygenase inhibitor indomethacin, through cannulization of the sublingual artery, caused a generalized reversible arteriolar vasoconstriction of 51 +/- 9.8% but did not inhibit the segmental vasodilator effect of locally microinjected L-lactate.

CONCLUSIONS

It is known that acute hypoxia in the isolated retina causes an increase in lactate production. In the intact eye, there is a retinal vasodilation, which is not inhibited by indomethacin. Hence, it was concluded that retinal, but not blood, lactate is a possible mediator of the acute hypoxia-induced vasodilation.

[Profile of pO2. I. Profile of transretinal pO2 in hypoxia]

Transretinal PO2 measurements during systemic hypoxia, made during variations of the PO2 by steps of 10 mmHg between 120 and 30 mmHg, have shown that the PO2 values measured at the inner-retina up to half the thickness of the retina remained stable. On the other hand, those measured at the choroid and at the outer-retina decreased in a linear manner according to the variations of PaO2. These results suggest a regulation in the retinal blood flow, allowing the PO2 to remain stable for the different steps of hypoxia studied. On the other hand, the values measured at the choroid and at the outer-retina showed the absence of regulation in the choroidal blood flow during hypoxia. Systemic hypoxia may affect the metabolism of the photoreceptors and the pigmentary epithelium.

[Profile of pO2. Regulation of papillary pO2]

PO2 measurements using a double barelled recess type microelectrodes were measured in the optic nerve head of miniature pigs during systemic hyperoxia (100% oxygen breathing) and variations of the systemic blood pressure by intravenous injection of Adrenaline or trinitrine. During either systemic hyperoxia, or progressive variations of blood pressure, the intervascular PO2 remained stable. These results suggest a regulation of the tissue PO2 of the optic nerve head, as the retina does, at constant values.

[Regulation of papillary pO2]

PO2 measurements using a double barelled recess type microelectrodes were measured in the optic nerve head of miniature pigs during systemic hyperoxia (100% oxygen breathing) and variations of the systemic blood pressure by intravenous injection of Adrenaline or trinitrine. During either systemic hyperoxia, or progressive variations of blood pressure, the intervascular PO2 remained stable. These results suggest a regulation of the tissue PO2 of the optic nerve head, as the retina does, at constant values.

[Metabolic factors of vasomotor regulation of the inner retina]

Lactic acid, the end metabolic product of anaerobic glycolysis is probably the mediator of the hypoxia induced vasodilation on retinal arterioles. In this study we explored the mechanisms of the retinal vasomotor effect of this metabolite by performing preretinal juxtaarteriolar pulsatile pressure microinjections on the intact eye of anesthetized and artificially ventilated miniature pigs. Microinjections of the levorotatory isomer L-lactic acid (pH: 2) induced a local maximal dilation of retinal arterioles. This vasodilator effect, like that of systemic hypoxia, was not mediated by the release of prostaglandins. Preretinal pulsatile pressure juxtaarteriolar microinjections of neutral-pH solution of L-lactic acid also induced a segmental retinal arteriolar dilation. In contrast, microinjections of the dextrorotatory isomer D-lactic acid (pH: 2, solution), which is not produced by the retina, did not affect significantly the arteriolar diameter. Consequently, the vasodilator effect of lactic acid does not depend on periarteriolar pH modification and probably interferes with retinal metabolism since only the natural levorotatory metabolite is recognized.

New ocular micromanipulator for measurements of retinal and vitreous physiologic parameters in the mammalian eye

A new ocular micromanipulator for introducing a microelectrode into the mammalian eye is described. Included is a technical description of the device, incorporating arched tracks and DC motors to provide for angular motion around a scleral entrance point. Applications for in vivo measurements of local PO2 in the retina and vitreous of miniature pigs and cats are shown. The new design features of this micromanipulator allow for smooth microelectrode movements over large retinal areas, facilitating the rapid collection of data in many different areas of the retina and vitreous.

[Regulation of PO2 in the area of the optic papilla of the minipig in hyperoxia]

PO2 measurements using a double barrelled recess type microelectrodes were measured in the optic nerve head of miniature pigs in normoxia and hyperoxia. Although periarteriolar PO2 increased markedly during systemic hyperoxia (100% oxygen breathing), the intervascular PO2 remained stable under hyperoxia. These results suggest a regulation of the tissue PO2 of the optic nerve head, as the retina does, at constant values during hyperoxia.

[Experimental venous branch occlusion: change in the preretinal oxygen pressure pO2 by dexamethasone]

Transretinal pO2 profiles were recorded during normoxia and hyperoxia in normal and ischemic retinal regions in anesthetized miniature pigs, using double-barrelled recess-type microelectrodes. In normoxia and hyperoxia, pO2 in the normal region decreased from the inner retina and the choroid toward the midretina, indicating that the choroid cannot supply O2 to the entire normal retina. Preretinal and transretinal pO2 measurements in ischemic regions following laser occlusion of a retinal branch vein showed that in normoxia the direction of pO2 gradients prevents O2 diffusing from the choroid to reach the inner retina. This explains why the ischemic regions remain hypoxic. On the contrary, during hyperoxia the intraretinal pO2 gradient indicates an O2 flux from the choroid to the inner retina, resulting in a marked increase in preretinal pO2 in the affected regions. Hence hyperoxia could be a useful tool for restoring the oxygen supply to the inner, hypoxic retinal layers; unfortunately it cannot be used in clinical practice. Parabulbar injections of dexamethasone induce a transitory increase in preretinal pO2, probably by reducing the outer retinal consumption of O2 and thus allowing O2 which diffuses through the choroid to reach and restore the inner retinal hypoxia; clinical experience has shown that parabulbar dexamethasone injections may be effective in the treatment of venous branch occlusion.

Quartz micropipettes for intracellular voltage microelectrodes and ion-selective microelectrodes

We find that quartz is better than borosilicate glass as a material for micropipettes for certain microelectrode applications, including ion-selective microelectrodes of the liquid membrane type. Details are given of a graphite heating element that can be mounted on a standard microelectrode puller and used for making quartz micropipettes. A novel method of silanizing micropipettes is described. Experience with a novel miniature beveller that is fitted on a microscope stage is reported.

In vitro human antibody production to the Haemophilus influenzae type b capsular polysaccharide

In vitro production of human antibody to the Haemophilus influenzae type b capsular polysaccharide (PRP) and to tetanus toxoid (TT) and diphtheria toxoid was measured in culture supernatants of peripheral blood mononuclear cells and by enumeration of antibody secreting cells (AbSC) in an enzyme-linked immunosorbent-plaquing assay. Normal adult peripheral blood mononuclear cells stimulated with Epstein-Barr virus secreted anti-PRP antibody with a frequency of 1/552 to 1/1190 relative to total Ig secreting cells; the frequency of AbSC to tetanus toxoid (TT) was 7.5 times higher (p less than 0.05). These frequencies did not change significantly after in vivo immunization, although the isotype distribution shifted toward increased IgG for TT and increased IgG and IgA for PRP. At 8 days postimmunization, spontaneous AbSC to PRP and TT were detected; frequencies for total anti-TT AbSC again being higher than anti-PRP, but there were significantly more IgA plaques among anti-PRP AbSC. Spontaneous AbSC were suppressed in culture by pokeweed mitogen and enhanced by cyclosporine. Three wk after in vivo immunization with PRP and TT, in vitro stimulation with pokeweed mitogen, Staphylococcus aureus Cowan 1 bacteria, or antigen induced anti-TT but not anti-PRP in vitro antibody secretion, although Epstein-Barr virus induced both. These data suggest that PRP, a polysaccharide, and TT, a protein, differ in their requirements for in vitro activation with antigen and mitogens.

In vitro human antibody production to the Haemophilus influenzae type b capsular polysaccharide

In vitro production of human antibody to the Haemophilus influenzae type b capsular polysaccharide (PRP) and to tetanus toxoid (TT) and diphtheria toxoid was measured in culture supernatants of peripheral blood mononuclear cells and by enumeration of antibody secreting cells (AbSC) in an enzyme-linked immunosorbent-plaquing assay. Normal adult peripheral blood mononuclear cells stimulated with Epstein-Barr virus secreted anti-PRP antibody with a frequency of 1/552 to 1/1190 relative to total Ig secreting cells; the frequency of AbSC to tetanus toxoid (TT) was 7.5 times higher (p less than 0.05). These frequencies did not change significantly after in vivo immunization, although the isotype distribution shifted toward increased IgG for TT and increased IgG and IgA for PRP. At 8 days postimmunization, spontaneous AbSC to PRP and TT were detected; frequencies for total anti-TT AbSC again being higher than anti-PRP, but there were significantly more IgA plaques among anti-PRP AbSC. Spontaneous AbSC were suppressed in culture by pokeweed mitogen and enhanced by cyclosporine. Three wk after in vivo immunization with PRP and TT, in vitro stimulation with pokeweed mitogen, Staphylococcus aureus Cowan 1 bacteria, or antigen induced anti-TT but not anti-PRP in vitro antibody secretion, although Epstein-Barr virus induced both. These data suggest that PRP, a polysaccharide, and TT, a protein, differ in their requirements for in vitro activation with antigen and mitogens.

Acid-base properties of human gingival crevicular fluid

The pH of human gingival crevicular fluid (GCF) has been reported by many authors to be very alkaline (pH 7.5 - 8.7). This alkalinity could be explained, at least partially, by the fact that all measurements were performed either at low PCO2 or in the absence of CO2. Therefore, we set up a procedure which allows for measurement of the pH of GCF samples from single inflamed sites at controlled PCO2. At a PCO2 of 4.7 kPa (= 35 mmHg) and at 37 degrees C, the pH was 7.96 +/- 0.10 (SEM, n = 9), a value which differs significantly from the value of 8.38 +/- 0.09 measured in the absence of CO2 in the same samples. The non-bicarbonate buffer value of the sample determined by CO2 titration was 6.0 slykes. It is because this value is low that pH varies so greatly with PCO2. At physiological PCO2, the total buffering power becomes very high above pH 8.0, because of the high bicarbonate concentration.

Silanization of glass in the making of ion-sensitive microelectrodes

The silanization of glass, particularly Pyrex, was studied using reaction conditions that might be applied in the fabrication of ion-sensitive microelectrodes of the liquid-membrane type. The efficacy was tested by measuring the hydrophobicity (contact angle) or electrical resistivity of the treated surface. Aminosilanes, such as trimethyl-(dimethylamino)-silane are better than chlorosilanes, the optimum temperature is 250-330 degrees C, and the reaction comes near to completion in 5 min. Silanization of glass that is newly exposed (as in the pulling of a micropipette) is greatly improved if the surface is treated with acid. There is considerable variation from one kind of glass to another. A recipe for making double-barrelled ion-sensitive microelectrodes is given.

Phospholipid biosynthesis and secretion by a cell line (A549) which resembles type II aleveolar epithelial cells

The A549 cell line is a continuous cell line derived from a human adenocarcinoma of the lung. At low cell population density the cells contain relatively few lamellar bodies, but in mature cells in very confluent cultures lamellar bodies are abundant. The lamellar bodies from these cells are enriched for phosphatidylcholine and disaturated phosphatidylcholine. In mature cells, 45% of newly synthesized phosphatidylcholine is disaturated. Stimulation with the calcium ionophore A23187 produces exocytosis of phosphatidylcholine (46% disaturated). The A549 cell synthesizes, stores in lamellar bodies, and secretes phosphatidylcholine, and thus has many important biological properties of the alveolar epithelial type II cell.