A comparison between hyaluronic acid and other single ingredient eye drops for dry eye, a review

Dry eye disease (DED) is a highly prevalent and debilitating condition. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan that has a long history as a safe and effective DED treatment. HA is frequently used as a comparator when assessing other topical DED treatments. This study aims to summarise and critically evaluate the literature describing all isolated active ingredients that have been directly compared with HA in the treatment of DED. A literature search was conducted in Embase using Ovid on the 24th of August 2021 and in PubMed including MEDLINE on the 20th of September 2021. Twenty-three studies met the inclusion criteria, 21 of which were randomised controlled trials. Seventeen different ingredients representing six treatment categories were compared with HA treatment. Most measures showed no significant difference between treatments, suggesting either equivalency of treatments or that studies were underpowered. Only two ingredients were represented in more than two studies; carboxymethyl cellulose treatment appears equivalent to HA treatment, while Diquafosol treatment appears superior to HA treatment. Drop-frequency varied from one to eight drops daily. No single study explained the choice of drop frequency. Nine studies used a HA concentration of 0.1% which may be below therapeutic levels. Nine studies reported using preserved formulations, six of them with differences in preservatives between the compared groups. Thirteen studies were financially linked to industry. No major complications were reported. Studies were not designed to find differences in treatment effects for different types or severities of DED. HA is a good comparator treatment when assessing other DED treatments, although consensus after decades of use is still lacking for best choice of concentration, molecular weight and drop tonicity. Well-designed studies are needed to determine an evidence-based standard for HA treatment to be used as comparator.

Review on the possible pathophysiological mechanisms underlying visual display terminal-associated dry eye disease

BACKGROUND

Visual display terminal (VDT) use is a key risk factor for dry eye disease (DED). Visual display terminal (VDT) use reduces the blink rate and increases the number of incomplete blinks. However, the exact mechanisms causing DED development from VDT use have yet to be clearly described.

PURPOSE

The purpose of the study was to conduct a review on pathophysiological mechanisms promoting VDT-associated DED.

METHODS

A PubMed search of the literature investigating the relationship between dry eye and VDT was performed, and relevance to pathophysiology of DED was evaluated.

FINDINGS

Fifty-five articles met the inclusion criteria. Several pathophysiological mechanisms were examined, and multiple hypotheses were extracted from the articles. Visual display terminal (VDT) use causes DED mainly through impaired blinking patterns. Changes in parasympathetic signalling and increased exposure to blue light, which could disrupt ocular homeostasis, were proposed in some studies but lack sufficient scientific support. Together, these changes may lead to a reduced function of the tear film, lacrimal gland, goblet cells and meibomian glands, all contributing to DED development.

CONCLUSION

Visual display terminal (VDT) use appears to induce DED through both direct and indirect routes. Decreased blink rates and increased incomplete blinks increase the exposed ocular evaporative area and inhibit lipid distribution from meibomian glands. Although not adequately investigated, changes in parasympathetic signalling may impair lacrimal gland and goblet cell function, promoting tear film instability. More studies are needed to better target and improve the treatment and prevention of VDT-associated DED.

Hyaluronic acid in the treatment of dry eye disease

Dry eye disease (DED) is a highly prevalent and debilitating condition affecting several hundred million people worldwide. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan commonly used in the treatment of DED. This review aims to critically evaluate the literature on the safety and efficacy of artificial tears containing HA used in DED treatment. Literature searches were conducted in PubMed, including MEDLINE, and in Embase via Ovid with the search term: "(hyaluronic acid OR hyaluronan OR hyaluronate) AND (dry eye OR sicca)". A total of 53 clinical trials are included in this review, including eight placebo-controlled trials. Hyaluronic acid concentrations ranged from 0.1% to 0.4%. Studies lasted up to 3 months. A broad spectrum of DED types and severities was represented in the reviewed literature. No major complications or adverse events were reported. Artificial tears containing 0.1% to 0.4% HA were effective at improving both signs and symptoms of DED. Two major gaps in the literature have been identified: 1. no study investigated the ideal drop frequency for HA-containing eyedrops, and 2. insufficient evidence was presented to recommend any specific HA formulation over another. Future investigations assessing the optimal drop frequency for different concentrations and molecular weights of HA, different drop formulations, including tonicity, and accounting for DED severity and aetiology are essential for an evidence-based, individualized approach to DED treatment.

Hyaluronic acid in the treatment of dry eye disease

Dry eye disease (DED) is a highly prevalent and debilitating condition affecting several hundred million people worldwide. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan commonly used in the treatment of DED. This review aims to critically evaluate the literature on the safety and efficacy of artificial tears containing HA used in DED treatment. Literature searches were conducted in PubMed, including MEDLINE, and in Embase via Ovid with the search term: "(hyaluronic acid OR hyaluronan OR hyaluronate) AND (dry eye OR sicca)". A total of 53 clinical trials are included in this review, including eight placebo-controlled trials. Hyaluronic acid concentrations ranged from 0.1% to 0.4%. Studies lasted up to 3 months. A broad spectrum of DED types and severities was represented in the reviewed literature. No major complications or adverse events were reported. Artificial tears containing 0.1% to 0.4% HA were effective at improving both signs and symptoms of DED. Two major gaps in the literature have been identified: 1. no study investigated the ideal drop frequency for HA-containing eyedrops, and 2. insufficient evidence was presented to recommend any specific HA formulation over another. Future investigations assessing the optimal drop frequency for different concentrations and molecular weights of HA, different drop formulations, including tonicity, and accounting for DED severity and aetiology are essential for an evidence-based, individualized approach to DED treatment.

Review on the possible pathophysiological mechanisms underlying visual display terminal-associated dry eye disease

BACKGROUND

Visual display terminal (VDT) use is a key risk factor for dry eye disease (DED). Visual display terminal (VDT) use reduces the blink rate and increases the number of incomplete blinks. However, the exact mechanisms causing DED development from VDT use have yet to be clearly described.

PURPOSE

The purpose of the study was to conduct a review on pathophysiological mechanisms promoting VDT-associated DED.

METHODS

A PubMed search of the literature investigating the relationship between dry eye and VDT was performed, and relevance to pathophysiology of DED was evaluated.

FINDINGS

Fifty-five articles met the inclusion criteria. Several pathophysiological mechanisms were examined, and multiple hypotheses were extracted from the articles. Visual display terminal (VDT) use causes DED mainly through impaired blinking patterns. Changes in parasympathetic signalling and increased exposure to blue light, which could disrupt ocular homeostasis, were proposed in some studies but lack sufficient scientific support. Together, these changes may lead to a reduced function of the tear film, lacrimal gland, goblet cells and meibomian glands, all contributing to DED development.

CONCLUSION

Visual display terminal (VDT) use appears to induce DED through both direct and indirect routes. Decreased blink rates and increased incomplete blinks increase the exposed ocular evaporative area and inhibit lipid distribution from meibomian glands. Although not adequately investigated, changes in parasympathetic signalling may impair lacrimal gland and goblet cell function, promoting tear film instability. More studies are needed to better target and improve the treatment and prevention of VDT-associated DED.

Video display terminal use and dry eye: preventive measures and future perspectives

BACKGROUND

Dry eye disease (DED) is a common cause of ocular pain and discomfort. Dry eye disease (DED) stems from a loss-of-tear film homeostasis and is frequently seen in video display terminal (VDT) users. Video display terminal (VDT) use reduces blink rates and increases incomplete blinks, leading to tear film instability and ocular inflammation, promoting DED.

PURPOSE

To assess and evaluate the methods for preventing VDT-associated DED and ocular discomfort.

METHODS

Studies were found using PubMed and Embase with the search terms: (digital visual terminal* OR computer use OR screen use OR smartphone OR display OR visual display terminal* OR computer vision syndrome OR tablet OR phone OR screen time) AND (dry eye OR DED).

RESULTS

Thirty-one relevant articles were found. Ten described single-visit studies, whereas 21 had a prolonged follow-up. Most preventive measures of VDT-associated DED aimed to increase blink rate or directly prevent tear film instability, ocular inflammation, mucin loss or ocular surface damage. Using an adjustable chair and ergonomic training, blink animations and omega-3 supplementation improved signs and symptoms of VDT-associated DED. Taking frequent breaks was associated with fewer symptoms, but no study assessed the commonly suggested 20-20-20 rule.

CONCLUSION

Preventive measures, such as blink animation programmes, oral intake of omega-3 fatty acids and improved ergonomics act on different parts of the vicious cycle of dry eye and could supplement each other. A comparison of the efficacy of the different interventions as well as more evidence of the effect of increased humidity, VDT filters and ergonomic practices, are required.

The association between visual display terminal use and dry eye: a review

BACKGROUND

Dry eye disease (DED) is a multifactorial disease of the tear film and ocular surface. It causes ocular symptoms, reduced quality of life and a considerable economic burden on society. Prolonged use of visual display terminals (VDTs) has been suggested as an important risk factor for DED.

PURPOSE

This review aims to study the association between DED and VDT use with an emphasis on the prevalence of DED among VDT users and harmful daily duration of VDT use.

METHODS

A PubMed search was conducted and yielded 57 relevant articles based on a set of inclusion and exclusion criteria. The studies were subclassified according to study design.

RESULTS

The far majority of the studies showed an association between VDT use and DED or DED-related signs and symptoms. The prevalence of definite or probable DED in VDT and office workers ranged from 26% to 70%, with as few as 1-2 hr of VDT exposure per day being associated with DED.

CONCLUSION

VDT use is strongly associated with DED. VDT-associated DED is prevalent, but the exact prevalence needs to be further elucidated using standardized DED diagnosis criteria. Furthermore, a safe lower limit of daily VDT use has yet to be established. More research is needed on the effect of digitalization and digital transformation, which are particularly high during the time of the COVID-19 pandemic.

Intraductal meibomian gland probing and its efficacy in the treatment of meibomian gland dysfunction

Meibomian gland dysfunction (MGD) is a major cause of dry eye, affecting millions worldwide. Intraductal meibomian gland probing (MGP) aims to open obstructed meibomian glands using a small probe to promote meibum secretion. MGP has received increasing interest since 2010, and we critically evaluated the literature on the efficacy and safety of MGP. Despite positive results of MGP on dry eye symptoms in early single-group studies, MGP was not shown to consistently outperform controls in later controlled trials. Furthermore, MGP alone did not show improvement beyond placebo in the only placebo-controlled RCT conducted. Overall, the procedure appears safe. Self-limited intraoperative bleeding was frequent, but no major complications were reported. In conclusion, MGP has not yet been shown to be an effective treatment for MGD. Larger placebo-controlled trials need to be conducted to establish the potential effect of this novel treatment modality.

Myofibroblast involvement in glycosaminoglycan synthesis and lipid retention during coronary repair

Myofibroblasts of adventitial origin have been linked to neointimal formation and remodeling after coronary injury. Accordingly, the goal of this study was to examine whether myofibroblasts contribute to focal accumulation of glycosaminoglycans (GAGs) and lipids during coronary repair. GAG synthesis was assessed by ex vivo labeling of balloon-injured porcine coronary arteries with (14)C-glucosamine. The synthesis of total GAGs transiently increased at 8 days in the normolipemic model (a 2.2-fold increase over baseline, p < 0.05). The majority of newly synthesized GAGs were sensitive to chondroitin ABC lyase (chondroitin/dermatan sulfate GAGs). Versican was localized to myofibroblast-rich regions in the adventitia and neointima [positive for alpha-smooth muscle (SM) actin, negative for h-caldesmon and SM myosin heavy chain]. In contrast, the adjacent SM-rich media showed no increase in versican expression. The association between injury-induced GAG accumulation and lipid retention was examined at 2 weeks after coronary injury in the hyperlipemic model. Lipid (Oil Red O) accumulated in the neointima and adventitia, but not in the adjacent media. Coronary repair under hyperlipemic conditions was associated with macrophage infiltration (19 +/- 5 vs. 3 +/- 2% of neointimal cells in normolipemic animals, p < 0.001) and increased neointimal formation (1.8 +/- 0.5 vs. 1.0 +/- 0.3 mm(2) in normolipemic animals, p < 0.01). In conclusion, this study demonstrated a transient increase in GAG synthesis following coronary injury. Chondroitin sulfate proteoglycans (e.g., versican) were rapidly synthesized by activated adventitial and neointimal cells which could contribute to early lipid retention in injured vessels.

Cardiomyoplasty

Cardiomyoplasty is a new surgical treatment for heart failure in which skeletal muscle assists the heart. However, for the first 2 weeks postoperatively, the latissimus dorsi muscle (LDM) remains unstimulated, and during the next 2 weeks, the LDM is stimulated with only one pulse every other heart beat. Thus, for the initial 4 postoperative weeks, minimal systolic assistance is provided. The present study determined if the LDM is capable of providing early assistance. Cardiomyoplasty surgery involves severing the perforating intercostal arteries to the LDM, detaching the LDM from its distal insertion, and wrapping it around the heart. At each of these steps, we measured LDM force development, shortening, and blood flow in six dogs. At control, LDM shortening, work, and power decreased during a 2 min fatigue test: fatigue indices (final/ initial value) for shortening, work, and power were 47.6 +/- 6.9%, 47.5 +/- 7.1%, and 46.9 +/- 6.6%, respectively. Blood flow increased in the proximal (P), mid (M), and distal (D) LDM during the fatigue test. After partial vascular isolation, initial shortening, work, and power decreased by 29.4%, 32.5%, and 31.7% from their respective control values. During the fatigue test, fatigue indices for shortening, work, and power were 24.7 +/- 3.3%, 19.5 +/- 4.6%, and 22.2 +/- 4.7%, respectively, all significantly (p < 0.05) less than control values. Resting blood flows were unaltered. During exercise, flow to the P increased, whereas flow did not increase in M (p < 0.05). Loss of LDM function was most apparent after mobilizing and reattaching the muscle. Initial shortening, work, and power significantly decreased (p < 0.05) by 74.1%, 76.8%, and 74.4%, from their respective control values. During a fatigue test, final values for shortening, work, and power were all near zero. Resting blood flow decreased in the M and D (p < 0.05) and, during exercise, blood flow increased only in P. Thus, LDM function was severely depressed during the isolation procedure. This functional loss is associated with inadequate blood flow responses. Therefore, preconditioning and/or revascularization is needed if the LDM is to provide cardiac assistance shortly after cardiomyoplasty surgery.

Cytophagocytosis by the blast cells in acute myeloid leukemia

The occurrence of cytophagocytosis as spontaneous ingestion of cells by blast cells has been poorly investigated in acute leukemia. Cytophagocytosis by blasts in acute myeloid leukemia (AML) was observed in eleven patients who represent 1% of AML cases seen in our institution (one M1, two M2, four M4 and four M5). Prominent features of cytophagocytosis by AML blasts are particularly evident in leukemias involving monocytic cells and were more obvious in the bone marrow than the peripheral blood. AML of the monocytic type with cytophagocytosis are frequently associated with cytogenetic aberrations involving chromosomes 8 and 16. Finally the poor outcome of AML patients with cytophagocytosis and their poor response to therapy and short survival is stressed.

Techniques to enhance extramyocardial collateral blood flow after a cardiomyoplasty

OBJECTIVE

Chronic stimulation of a cardiomyoplasty was combined with low-dose infusion of heparin into the arterial supply of the cardiomyoplasty in order to determine if latissimus-derived collateral blood flow could be further enhanced.

SUMMARY BACKGROUND DATA

Acute and chronic stimulation of a latissimus dorsi cardiomyoplasty increased extramyocardial collateral blood flow to 35 +/- 9% and 27 +/- 5%, respectively, of normal myocardial blood flow.

METHODS

A model of coronary artery disease was created with an ameroid constrictor in goats, and a cardiomyoplasty was performed. Heparin (15 to 50 U/h) was delivered into the left subclavian artery for a period of 4 weeks. Simultaneously, the latissimus dorsi was chronically stimulated at 2 Hz.

RESULTS

Chronic ischemic myocardium received a collateral flow per gram from the skeletal muscle equivalent to 11.8 +/- 5.2% of the blood flow to normal myocardium. The extramyocardial collateral flow correlated with the latissimus muscle flow (r = 0.72).

CONCLUSIONS

Enhancement of extramyocardial collateral flow was not found with heparin treatment. In view of the correlation of extra-coronary collateral flow with latissimus muscle flow, the lack of a heparin effect may have been due to low latissimus blood flow. These results suggest that extramyocardial collateral blood flow to the myocardium is highest if the blood flow to the latissimus dorsi muscle is maintained.

After a cardiomyoplasty, collaterals from skeletal muscle form to chronic ischemic myocardium

We measured the collateral formation between skeletal muscle and the heart after a latissimus dorsi cardiomyoplasty in an animal model that contained normal, chronic ischemic, and infarcted myocardium. The area at risk for ischemia was 27.0 +/- 3.2% of the left ventricular mass (n = 10, mean +/- SE). In five animals the risk area developed predominantly into chronic ischemic myocardium; in five others the risk area became an infarct. The collateral blood flow from the skeletal muscle to chronic ischemic myocardium (6.05 +/- 1.36 ml/100 g/min, n = 5) was higher than flow to the infarct (0.46 +/- 0.31 ml/100 g/min, n = 5). The collateral blood flow to normal myocardium was minimal (0.04 +/- 0.01 ml/100 g/min). The collateral blood flow appeared to be concentrated in the outer half of the left ventricular wall, with the epicardium having a higher skeletal muscle derived collateral blood flow than endocardium (p < 0.05). We conclude that after a cardiomyoplasty a collateral blood flow, which approaches clinical significance, is preferentially established between skeletal muscle and chronic ischemic myocardium. Enhancement of this collateral blood flow might provide a means to revascularize patients with presently inoperable coronary disease.

Influence of bronchial arterial PO2 on pulmonary vascular resistance

In six anesthetized and mechanically ventilated adult sheep, the bronchial artery was perfused with blood from an oxygenator-pump circuit. When the lungs were ventilated with 100% O2 and the bronchial O2 tension (PbrO2) was approximately 600 Torr, the mean of the pulmonary vascular resistances (PVR) measured at the beginning (3.32 +/- 0.29 units) and end (3.17 +/- 0.13 units) of the experiment was 3.24 +/- 0.20 units. When the PbrO2 was changed to 58 +/- 1 Torr, the PVR (2.99 +/- 0.14 units) did not change significantly. However, when the lungs were ventilated with air as PbrO2 was decreased to 91 +/- 4, 77 +/- 3, 56 +/- 2, and 42 +/- 1 Torr, the PVR increased to 3.67 +/- 0.18, 4.03 +/- 0.16, 4.79 +/- 0.19, and 4.71 +/- 0.35 units, respectively. However, when the PbrO2 was decreased further to 26 +/- 1 and 13 +/- 1 Torr, the PVR decreased to 3.77 +/- 0.28 and 3.91 +/- 0.30 units, respectively. In contrast, the bronchial vascular resistance decreased monotonically as PbrO2 decreased. The bronchial circulation supplies vasa vasorum to the walls of all but the smallest pulmonary arteries, and it is therefore suggested that the PO2 of the bronchial circulation is responsible for the bimodal response of the pulmonary vasculature, with stimulation of hypoxic pulmonary vasoconstriction at moderate hypoxemia and of hypoxic pulmonary vasodilation at profound hypoxemia. The physiological and pathophysiological significance of the influence of systemic PO2 on pulmonary vascular tone is discussed.

Analysis of diabetic family connection in subjects with insulin-dependent diabetes mellitus (IDDM)

The family connection of diabetes was examined from the clinical records of 3,372 subjects who were seen, as an out patient population, within the frame of a Regional Health Program in Taranto, South Italy. The family connection of diabetes resulted from a questionnaire in which the subjects had to give informations about their disease, if present, and degrees of relationship that were directly verified by us with the examination (clinic and laboratory) of relatives said to have diabetes. From the analysis of records, it emerged that 112 patients were affected by insulin-dependent-diabetes mellitus (IDDM): 54 of them were related with at least one subject suffering from noninsulin-dependent diabetes mellitus (NIDDM), 13 with at least one subject affected by IDDM and the remaining 45 did not show any family connection. The corresponding figures found in a group of healthy control subjects, matched to IDDM patients for age, sex and BMI, were 19, 2 and 84, respectively (p less than 0.001). 34 IDDM patients were related with a first degree of relationship (parents, sons, sibs) to diabetic subjects (IDDM or NIDDM), but only 4 controls showed such a degree (p less than 0.001). These results seem to indicate that patients with IDDM have an increased family history of NIDDM.

Hydroxychloroquine in decompensated, treatment-refractory noninsulin-dependent diabetes mellitus. A new job for an old drug?

STUDY OBJECTIVE

To evaluate the usefulness and safety of hydroxychloroquine in patients with decompensated, treatment-refractory noninsulin-dependent diabetes mellitus.

DESIGN

Prospective, randomized, placebo, double-blind 6-month trial.

PATIENTS

Thirty-eight patients with noninsulin-dependent diabetes resistant to commonly used therapies (oral drugs, insulin, combination of insulin and oral drugs).

INTERVENTIONS

Two study groups: one received insulin (n = 22) and the other, glibenclamide (n = 16). In each group, half of the patients were randomly allocated into two subgroups who continued the previous treatment but took either placebo tablets or hydroxychloroquine, 200 mg three times a day. The four subgroups were as follows: insulin and placebo (n = 11); insulin and hydroxychloroquine (n = 11); glibenclamide and placebo (n = 8); and glibenclamide and hydroxychloroquine (n = 8).

MEASUREMENTS AND MAIN RESULTS

At 6 months, relevant and statistically significant improvement occurred in the 11 patients who received the insulin and hydroxychloroquine (glucose profile decrease, -11.7 mmol/L; 95% CI, -13.9 to -9.5, P = 0.001; glycated hemoglobin A1c decrease, -3.3%; 95% CI, -3.9 to -2.7, P = 0.001). No significant changes were seen in patients on placebo. The daily insulin dose in patients treated with the combined insulin and hydroxychloroquine therapy had to be reduced an average of 30%. No important side effects were detected.

CONCLUSIONS

Combining antidiabetic therapy with hydroxychloroquine in decompensated, treatment-refractory patients with noninsulin-dependent diabetes may help to break the vicious circle of hyperglycemia and lead to better management of the disease.

Carotid body control of bronchial circulation in sheep

The bronchial vascular response to chemoreceptor stimulation was studied in sheep anesthetized with alpha-chloralose, paralyzed with pancuronium, and artificially ventilated with room air. Blood flow through the common bronchial artery was measured with an electromagnetic flow-meter. Pressures were measured in the left atrium and aorta using appropriately placed catheters connected to pressure transducers. The carotid body was vascularly isolated and perfused at aortic pressure with blood of varied PO2 and PCO2. The viability of our preparation was assessed by the occurrence of a bradycardia in response to carotid body stimulation, and only data from animals demonstrating a bradycardia were analyzed. During hypoxic perfusion of the carotid body, heart rate decreased 6% (P less than 0.05). Bronchial blood flow increased by 46% and bronchial vascular resistance decreased by 23%, both of which were significant changes (P less than 0.05). During control experiments in which the carotid body was perfused with normoxic blood, there were no significant (P greater than 0.05) changes in any of the parameters. These data suggest that carotid body stimulation results in a reflex bronchial vasodilation.

Acute lymphoblastic leukemia hand-mirror cells with OKT 8 phenotype

Acute lymphoblastic leukemia with hand-mirror cells (ALL-HMC) was diagnosed in a 20-year old patient. Cytochemical investigations revealed a positive reaction for PAS and acid phosphatase. Lymphoid blast cells were studied with various monoclonal antibodies in order to determine their derivation and differentiation. The data obtained (positivity for Leu 9, OKT 11 and OKT 8) suggest that blast cells were of T lineage with OKT 8 phenotype. This report supports the phenotypic heterogeneity of ALL-HMC.

[Characteristics of the electrophoretic mobility of blasts from acute non-lymphoid leukemias]

The behaviour of electrophoretic mobility (E.M.) of the blast cells has been investigated in 15 cases of acute non lymphoid leukemias (A.N.L.L.), (eleven cases of M1 type and four M5 type). The fast and homogeneous E.M. of M5 type in comparison with M1 has been underlined. E.M. of M1 blasts has been reported in a wide range varying from a "normal" migration (similar to that of normal neutrophils and monocytes) to a "fast" one (similar to M5 type). It is suggested that M1 leukemic forms, morphologically recognizable as the same leukemic type, are different L.A.N.L. indeed.

Fusion of pinocytotic vesicles in liquid filled lungs: a mechanism of cellular damage

Lungs of anesthetized rabbits were filled unilaterally with macromolecule-containing solutions (Dextran 40 and albumin) for 20 min. which generally resulted in fluid resorption from the flooded lung. Electron microscopic examination revealed the following: (1) formation of chains of vesicles, similar or identical to pinocytotic vesicles, which start from depressions or fluid-immersed cellular surfaces in macrophages, or endothelial and squamous epithelial cells; and (2) formation of intracellular blisters as a result of the apparent fusion of numerous pinocytotic vesicles. Both observations seem to be augmented forms of normal phenomena. The hypothesis is advanced that the chains of vesicles are related to the increased amount of undulation of the cell surface and to cellular invaginations that follow relaxation of tensions at the surface of cells immersed in fluid. The blisters could be the result of the increase of bidirectional flow of vesicles across the squamous cells. This brings an increased risk of collision because of the absence of lysosomes in the thin cytoplasmic extensions of endothelial and squamous epithelial cells. It is concluded that, even in very early stages, flooding per se produced some form of cellular alterations with a potential for leading to more overt lung pathology such as cell death and desquamation which would greatly increase tissue permeability.

Morphological and physiological study of the effect of histamine on the isolated perfused rabbit lung

Histamine causes interstitial pulmonary edema, but whether this is the result of an increased permeability of the pulmonary circulation or only of the bronchial circulation remains to be determined. In order to selectively study the effect of histamine on the pulmonary circulation, we used an isolated perfused rabbit lung preparation because in this species, the bronchial circulation is poorly developed. Edema formation was assessed by continuously monitoring the weight of the lung perfused at constant pressure. These studies were supplemented by electron microscopic observations using hemoglobin as an ultrastructural tracer for microvascular permeability. We found that histamine (8.0 microgram base/100 ml of perfusate) did not cause lung weight to increase. Ultrastructural studies showed that histamine, at this dosage, did not cause a greater leakage of hemoglobin that occurred in the control lungs. Thus, we have concluded that histamine does not increase the permeability of the pulmonary microcirculation in the isolated perfused rabbit lung.

Pharmacological factors influencing permeability of the bronchial microcirculation

The bronchial microcirculation is organized as a network of interconnected superficial and deep small blood vessels that extend throughout the bronchial tree. The close proximity of the bronchial venules to the origin of the pulmonary lymphatics suggests a role in fluid balance in the lung. The responsiveness of the venous segment of this network to agents influencing permeability clearly indicates a role in the genesis of certain types of noncardiogenic interstitial edema. The responsiveness of the venous segment of the bronchial circulation to neural and humoral stimuli raises the possibility of a significant role in the distribution of blood flow between the mucosa and peribronchial space. Such control may play a significant role in heat and water exchange between blood and air. Thus, these observations indicate that the bronchial microcirculation is involved with aspects of pulmonary function other than the nutrition of the bronchi, nerves, pleura, and large pulmonary blood vessels.

Cytochemical "normal" and "abnormal" eosinophils in acute leukemias

Eosinophilic leukocytes may accompany a great variety of disorders and different types of acute leukemias. The most striking morphologic feature of eosinophils is their specific granules, but morphology alone often is insufficient to differentiate normal from abnormal eosinophils. Cytochemically, the eosinophils were considered "normal" when they did not contain alkaline phosphatase, chloroacetate esterase, toluidine blue metachromasia, Astra blue positivity, and specific PAS-positive granules, but did have peroxidase and cyanide-resistant peroxidase activities, Sudan black positivity and moderate naphthol-AS esterase or alpha-naphthyl esterase and acid phosphatase positivities. In seven cases of acute leukemias (two acute myeloblastic and five myelomonocytic), in contrast with their normal behaviour, the eosinophils show "abnormal" cytochemical positivities consisting of chloroesterase activity, PAS and Astra blue positivities of the specific granules, toluidine blue metachromasia, and cyanide-resistant peroxidase of a few specific granules. Cytochemical investigations may provide additional criteria for evaluating the abnormality of the eosinophilic cell in leukemias.

Hemodynamic pulmonary edema in dogs with acute and chronic lymphatic ligation

The effect of lymphatic ligation on relative lung water (g H2O/g dry lung) was studied in dogs. Raising left atrial pressure to 20 mmHg for 2 h in chronically lymphatic-ligated dogs (4 days) caused a significantly greater increase in relative lung water than the same hemodynamic challenge did in sham-operated and acutely lymphatic-ligated dogs. There was no significant difference in relative lung water between the acutely lymphatic-ligated and sham-operated dogs. At normal left atrial pressures, there was no significant difference in relative lung water between the sham-operated and chronically lymphatic-ligated dogs. Since the combined effects of chronic lymphatic ligation and left atrial hypertension is greater than the sum of the individual effects, it appears that chronic lymphatic ligation increases the susceptibility of the lung to hemodynamic edema, we suggest that chronic lymphatic ligation may have produced increases in the interstitial volume and protein mass that are undetectable by our technique. These increases, in turn, could lead to a reduction in tissue safety factors against hemodynamic pulmonary edema.