Pulmonary endothelial dysfunction induced by unilateral as compared to bilateral thoracic irradiation in rats

Rats were sacrificed 2 months after a single dose of 10-30 Gy of 60Co gamma rays delivered to either a right unilateral or a bilateral thoracic port. Four indices of lung endothelial function were measured: the activities of angiotensin-converting enzyme (ACE) and plasminogen activator (PLA) and the production of prostacyclin (PGI2) and thromboxane (TXA2). The number of macrophages recovered by bronchoalveolar lavage (BAL) and the degree of right ventricular hypertrophy (an index of pulmonary hypertension) also were determined. Right lung ACE and PLA activity decreased linearly, and PGI2 and TXA2 production increased linearly with increasing radiation dose. The response curves for right unilateral and bilateral thoracic irradiation were not significantly different. In contrast, bilateral irradiation was more toxic than unilateral, since rats exposed to the former exhibited decreased body weight, an increased incidence of pleural effusions, an increase in the number of macrophages recovered by BAL, and right ventricular hypertrophy. These data demonstrate that pulmonary endothelial dysfunction induced by hemithorax irradiation represents a direct response of the endothelium to radiation injury and is not secondary to other phenomena such as shunting of function to the shielded lung.

Vascular changes in popliteal lymph nodes due to antigen challenge in normal and lethally irradiated mice

The microvascular system of the murine popliteal lymph node was investigated using scanning electron microscopy of microcorrosion casts. Time-dependent changes in the microvasculature following regional antigen challenge in normal and lymphocyte-depleted mice were studied. Normal lymph node microvasculature exhibited a significant increase in both the vascular bed and post-capillary venules containing high-endothelium in response to antigen challenge. Lymph nodes of lymphocyte-depleted mice showed no microvascular size increase following antigen challenge and a reduction in the amount of high-endothelium was observed.

Radiosensitivity and sublethal damage repair in human umbilical cord vein endothelial cells

The assessment of the comparative radiosensitivity of different parenchymal cells is potentially of great importance in clinical radiotherapy. Previous studies from various laboratories using vessel regeneration techniques have demonstrated that endothelial cells are quite radioresistant, having a Do in excess of 250 rads. The present studies were undertaken to investigate the radiosensitivity of human endothelial cells obtained from umbilical cord veins (HEC) using "colony formation" as an endpoint, and to evaluate their ability to repair sublethal radiation damage (SLD). The endothelial origin of the cells in the surviving colonies was demonstrated by their positive staining for factor VIII antigen. The survival curve for HEC has a Do of about 165 rads, with a moderate initial shoulder. Dose fractionation studies demonstrate a moderate capability to repair SLD, comparable to other human cells studied including fibroblasts and other normal diploid cells in vitro. These studies indicate that HEC, being a terminally differentiated cell type with various differentiated markers, may prove useful in radiobiological and radiocarcinogenesis studies.

Changes in lung morphology and cell number in radiation pneumonitis and fibrosis: a quantitative ultrastructural study

We used stereologic-morphometric techniques to obtain a detailed quantitative picture of the changes in lung ultrastructure of rats at 12 and 26 weeks after unilateral thoracic irradiation with 3000 cGy. At 12 weeks post-radiation, the total number type 1 epithelial cells, type 2 epithelial cells and capillary endothelial cells were decreased 50-70%, total type 1 epithelial and capillary surface areas were decreased 55-60%, and the total volume of intracapillary blood was decreased 75%. The interstitial cells and matrix together accounted for more than 9% of the peripheral lung tissue volume including air, compared to 3% in controls. The numerical density of interstitial cells was increased to 3-fold the control value. The numerical density of interstitial cells was increased to 3-fold the control value. Although fibroblasts still comprised the largest interstitial cell subgroup, the numerical density of mast cells was increased over 150-fold and other inflammatory and immune cells were increased to a lesser extent. At 26 weeks post-radiation, the number, volume, and surface area of the type 1 epithelium and capillary endothelium had further decreased to only 5-10% of control values. The total number of type 2 epithelial cells was reduced by 75% but the volume density was actually increased because of a 4-fold increase in the mean cell volume. The interstitial cells and matrix now comprised over 77% of total peripheral lung tissue volume including air as compared to 6% in controls. Mast cells and plasma cells comprised 11% and 19% of all interstitial cells respectively and the densities of these cells were 540 and 180-fold the control value respectively. The relation of these morphometric findings to the results of previous morphologic studies is discussed.

Laser-induced endothelial damage inhibits endothelium-dependent relaxation in the cerebral microcirculation of the mouse

This study demonstrates endothelium-dependent relaxation in the surface arterioles of the brain. A helium-neon laser was used to injure endothelium in situ following i.v. injection of Evans blue dye, which sensitizes the bed to the laser. Areas 18 or 36 micron in diameter were injured and no longer relaxed to either 1 ml of acetylcholine chloride or bradykinin triacetate, 80 micrograms/ml delivered for 60 seconds. Dilations to sodium nitroprusside (30 micrograms/ml) were unaffected. Normal responses to nitroprusside, plus electron microscopy, established that vascular smooth muscle was uninjured. Endothelium-dependent relaxation was impaired when only minor ultrastructural damage was present. Dilation was inhibited downstream and upstream as far as 80 micron from the center of the laser beam. This suggests a spread of endothelium injury around the site of laser impact. However, inhibition was somewhat more marked downstream than upstream, implying that a portion of the downstream response was dependent on a substance released from an upstream site. To date, very few studies have reported endothelium-dependent relaxation in vivo, especially in the microcirculation. The present study accomplishes this. Moreover, in contrast to in vitro observations of endothelium-dependent relaxation in large vessels, the in vivo elimination of endothelium-dependent relaxation in the microcirculation required neither removal of endothelium nor injury to large numbers of endothelium cells. Since endothelium-dependent relaxation in the microcirculation has now been demonstrated using three different techniques to injure endothelium, it is reasonable to conclude that the phenomenon is real.

[Morphologic examination of the urothelium after irradiation with laser energy]

The energy of a Nd-YAG laser (1,064 nm wave length, 8 ns pulse duration) was used to irradiate the urothelium of the ureter or bladder and kidney parenchyma in pigs. Single pulse energy was 50-120 mJ with a 20-Hz repetition rate. The horizontal laser beam was reflected 90 degrees down by a 100% mirror and with a specially designed apparatus focussed on the surface of the tissue. Laser light from a quartz glass fiber was also focussed directly onto the tissue. Urothelium and kidney parenchyma were irradiated in 7 pigs. Tissue samples were examined histologically and raster electron microscopically 2, 4, 8 and 12 days after irradiation. No macroscopic lesion could be found. Maximum energy caused a small cone of 40 micron depth. No thermic effects or necrosis resulted, so that no harm is to be expected with unintentional irradiation.

Cell cycle changes and cytotoxicity in irradiated cultures of bovine aortic endothelial cells

The purpose of this experiment was to determine the effect of ionizing radiation on cell number, lactate dehydrogenase (LDH) release, cell cycle distribution, [3H]thymidine incorporation, and autoradiographic labeling index in bovine aortic endothelial cells in vitro. Confluent endothelial monolayers were exposed to single doses of 0.5-10 Gy of 60Co gamma rays and were analyzed from 2 to 24 h postirradiation. Irradiated monolayers exhibited a time- and dose-dependent decrease in cell number, increase in LDH release, and redistribution of cells in the cell cycle. Cell cycle redistribution included an increase in the proportion of cells in S phase at 4 h after irradiation and a decrease in S phase at 24 h. The cells also exhibited a decrease in [3H]thymidine incorporation as early as 2 h after 5 Gy. This represented the most rapid radiation response observed in the present study. These data demonstrate that radiation cytotoxicity in confluent, plateau-phase endothelial monolayers is accompanied by changes in the cell cycle distribution of adherent cells, and that reduced [3H]thymidine incorporation is an early marker of radiation injury in this clinically important cell type.

Effects of irradiation on endothelial cell-polymorphonuclear leukocyte interactions

Prominent early effects of irradiation include neutrophilic vasculitis and interstitial inflammation. To examine the role of the endothelium in these events, bovine aortic endothelial cells (EC) were irradiated (5 Gy) under ambient conditions followed by measurements of neutrophil chemotaxis toward conditioned media and adherence to EC. Neutrophil chemotactic activity increased at 4, 24, and 72 h in both the sham-treated (4.2 +/- 2.5, 15.2 +/- 4.8, and 20.0 +/- 2.7 microns, respectively) and irradiated EC-conditioned media (5.0 +/- 2.1, 18.7 +/- 4.5, and 24.1 +/- 3.4 microns, respectively), and the difference between them was significant at 72 h. The chemoattractant was trypsin sensitive, heat resistant, and chemotactic. It was not present in the EC sonicate. Adherence of neutrophils to EC that were irradiated 4 h earlier (19.3 +/- 4.2%) increased compared with controls (11.1 +/- 2.4%) and was similar to EC pretreated with zymosan-activated serum (22.0 +/- 4.0%), which is a potent inducer of adherence. Thus, following irradiation, bovine aortic EC have greater neutrophil chemotactic activity in their media and are more adherent to polymorphonuclear leukocytes.

[The Helium-neon laser effect on skin and oral mucosal tissue]

The biological effects of the helium-neon (He-Ne) laser on skin and oral mucosa were examined for the first time electron microscopically. Canine epidermis, gingiva and sublingual regions were subjected to treatment by the helium-neon laser with varying exposure times. The exposed tissues were excised immediately after radiation and studied with an electron microscope. Depending on the exposure times, ultrastructural alterations were observed such as cytoplasmic vesiculation and vacuolization, mitochondrial changes, dilation of the endoplasmic reticulum, the Golgi cisternae and other endomembranes of the keratinocytes. Furthermore, ultrastructural changes were seen in stromal cells, endothelial cells of the blood and lymphatic vessels, nerves, muscle cells and in the extracellular compartment of the lamina propria. The ultrastructural alterations of different cell and tissue structures following helium-neon laser radiation were compared with the effects induced by other types of lasers. The results are discussed in light of the stimulation of biological cell processes by low-energy lasers.

Radiation nephritis following total-body irradiation and cyclophosphamide in preparation for bone marrow transplantation

Two children prepared for bone marrow transplantation with total-body irradiation and cyclophosphamide developed hypertension, microscopic hematuria, proteinuria, diminished renal function, and anemia six months after transplantation. Light microscopy of the kidneys revealed mesangial expansion, glomerular capillary wall thickening, and lumenal thrombosis. Electron microscopy demonstrated widening of the subendothelial space due to the deposition of amorphous fluffy material. In one patient, immunofluorescence microscopy revealed glomerular capillary wall deposition of fibrin and immunoglobulins. The clinical and histologic findings support the diagnosis of radiation nephritis. Patients prepared for bone marrow transplantation with total-body irradiation and cyclophosphamide should be followed closely after transplantation for the development of hypertension, proteinuria, and renal insufficiency.

Complement activation and adult respiratory distress syndrome during intermittent flow apheresis procedures

We observed complement (C) activation during intermittent flow apheresis procedures (Haemonetics model 30) in four subjects, two of whom developed adult respiratory distress syndrome (ARDS). Actual C3 conversion during apheresis was illustrated by the finding of significantly elevated C3d levels (p less than 0.05) and of significantly increased alpha-1-antitrypsin/C3 ratios (p less than 0.05) in postapheresis serums. Similarly, marked granulocyte aggregating activity was found in these serums, indicative of the generation of significant amounts of the C-derived anaphylatoxin, C5a or C5a desarginine. A mean decrease of 59.75 percent in neutrophil count during the four procedures suggested sequestration of aggregated granulocytes in the pulmonary vasculature. Moreover, granulocytes activated by apheresis serums induced significant 51Cr leak from cultured human endothelial cells is vitro (p less than 0.001). We conclude that inflammatory C components produced during apheresis procedures may provoke granulocyte aggregation and embolization, leading to plugging of the pulmonary vasculature, and that apheresis-activated granulocytes may induce endothelial cytotoxicity, leading to the capillary leakage syndrome, characteristic of ARDS. Individual variability in C5a generation capacity or alterations in normal C5a clearing mechanisms may account for the low incidence of clinical C activation and true ARDS during apheresis. In these instances, high-dose steroids, which interfere with granulocyte-C interactions, may be beneficial.

Vascular irradiation damage: its cellular basis and likely consequences

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Radiation induced damage in the choroid plexus of the rat brain: a histological evaluation

Early and late histological changes have been investigated in the choroid plexus after the local irradiation of the brain of rats with single doses of 17 X 5-25 Gy of X-rays. Changes were seen in epithelial cells within 1 week of irradiation. This was characterized by vacuolation, blebbing and partial lysis of the cytoplasm. Oedema in the underlying connective tissue was also seen after 1 week. A marked reduction in the number of endothelial cells, lining the walls of blood vessels, was found after 12 weeks; the severity was dose related and increased with time after irradiation. Slight atrophy of the epithelium was seen after 12 weeks. The reduction in endothelial cell number was associated with an attempt at regeneration as indicated by endothelial nuclear enlargement, nuclear pairs or groups and by the appearance of mitotic figures. Evidence or epithelial regeneration was not seen until week 26. Interstitial fibrosis was seen from 26 weeks after irradiation with the severity being both dose and time related. These late fibrotic changes were associated with basal membrane thickening, degenerative changes in the tunica media of arterioles and the appearance of thrombi. These changes are compared and contrasted with those seen in other normal tissues after irradiation and are discussed in terms of their relevance to the development of late radiation damage to the central nervous system.

The proliferative and functional response of mouse bladder to treatment with radiation and cyclophosphamide

The response of the mouse bladder to cyclophosphamide (Cy) and radiation, used alone or in combination, has been assessed in order to investigate whether epithelial denudation is the primary step in the sequence of events leading to bladder dysfunction, as expressed by increased urination frequency. The response to the two agents when used singly is consistent with the epithelium being the target tissue. However, early Cy denudation of the epithelium accompanied by rapid epithelial turnover, does not influence the time of onset of radiation dose-related bladder damage. Thus it appears that denudation of the bladder epithelium is not necessarily the immediate precursor of radiation injury.

The relationship between endothelial dysfunction and collagen accumulation in irradiated rat lung

Male rats were killed 2 months (early fibrosis) or 6 months (peak fibrosis) after a range of single doses of 60Co gamma rays to the right hemithorax. Pulmonary arterial perfusion scans were performed at 2 months on animals scheduled for autopsy at 6 months. Lung angiotensin converting enzyme (ACE) activity was used to monitor endothelial function, and hydroxyproline (HP) concentration served as an index of interstitial collagen accumulation (fibrosis). ACE activity also was measured in right lung bronchoalveolar lavage (BAL) fluid and blood serum, to determine whether information obtained from a minimally invasive procedure might serve as an index or predictor of the severity of lung damage. Linear dose-response curves (r = 0.92-0.99) were obtained for right lung arterial perfusion, ACE activity and HP concentration. At 2 months, perfusion decreased 2.7% per Gy, ACE activity (per lung, per mg wet weight, or per mg protein) decreased 3.0-4.2% per Gy, and HP concentration (per g dry weight) increased 1.7% per Gy. At 6 months, the slopes of the response curves were virtually identical to those at 2 months; the Y intercept of the response curve for ACE activity was unchanged, whereas that for HP concentration was 50% higher at 6 than at 2 months. ACE activity and protein concentration in the BAL increased with increasing dose, but the variation within groups was too large, and the sensitivity was too low to serve as a reliable index of lung status. Serum ACE activity was independent of radiation dose at both autopsy times. Thus in rat lung, arterial perfusion, endothelial dysfunction and interstitial fibrosis exhibit similar but not identical radiosensitivities. The dose-effect curves for these three responses of the lung in situ change less than 5% per Gy over the dose range of 10-30 Gy, a smaller variation than would be predicted from endothelial cell survival data based on clonogenic assays in vitro or in vivo.

Toxicity of methods of implant material sterilization on corneal endothelium

The toxicity of different procedures utilized for the sterilization of intraocular implant material was assessed on the endothelium of organ-cultured porcine corneas. Polymethylmethacrylate lenses sterilized by treatment with sodium hydroxide (NaOH), ethylene oxide, formaldehyde, and gamma radiation were added to a culture medium containing normal porcine corneas. Considering the viability of endothelial cells, appearance of intracellular degenerative vacuoles, and denudation of corneal Descemet's membrane as criterion for the evaluation of toxicity of different methods of sterilization, the NaOH-treated lenses were found to be the least toxic to porcine corneal endothelium. Phase-contrast microscopy and vital staining of the endothelium permitted direct viewing of the endothelium aiding in the assessment of toxicity.

Secondary surgical and neodymium-YAG laser discissions

Between November 1978 and June 1984, 161 surgical and 102 neodymium-YAG laser discissions were performed. The incidence of discission in patients with a mean three-year follow-up after extracapsular surgery was 22.1% (39 of 176 eyes) after extracapsular cataract extraction alone and 14.5% (81 of 558 eyes) after extracapsular cataract extraction with intraocular lens implantation (P less than .02); the incidence was 25.5% (47 of 184 eyes) with the transiridectomy clip lens and 9.1% (33 of 364 eyes) with the posterior chamber lens (P less than .001). The average interval between cataract surgery and the discission was 2.4 years. The intraocular pressure was increased in 51% (48 eyes) of the eyes two to five hours after YAG laser discission and was unpredictable in most patients. After surgical discission, the intraocular pressure was increased on the first postoperative day in 13% (18 eyes) of the eyes. With surgical discission, significant complications included vitreous manipulation, wound leak, and intraocular inflammation. Intraocular lens pitting occurred in 20 patients undergoing YAG laser discission. Complications with both procedures included cystoid macular edema, retinal detachment, glaucoma, and closure of a previously adequate discission opening.

Endothelial damage thresholds for retrocorneal Q-switched neodymium:YAG laser pulses in monkeys

Laser pulses were focused within 1 mm of the rhesus monkey corneal endothelium using the Coherent Model 9900 laser at energies of 3, 6, 9, and 12 mJ. Sixteen slightly off-axis pulses were applied with no contact lens on the eye. Corneal damage was studied clinically and by scanning electron microscopy. Q-switched pulses of 12 mJ or less are not likely to damage the cornea if focused more than 0.75 mm from the endothelium. The retrocorneal focal distance for a 50% incidence of endothelial damage for 6, 9, and 12 mJ pulses was found to be less than 0.5 mm. For 3 mJ pulses, it was less than 0.25 mm. The severe early effect of suprathreshold pulses is edema of endothelial cells in a 0.2- to 0.6-mm diameter circular zone surrounding a small central pit through Descemet's membrane. At two months, irregular enlargement of endothelial cells surrounding and partially covering the persistent pit exists at sites of severe damage. The extent of the longer-term change is proportional to the severity of the original insult, but in no case was there clinically significant, persistent damage in the healed corneas.

Increased accumulation of lipoprotein and cholesterol in re-endothelialized rat carotid artery after laser damage

The permeability characteristics of acute endothelial lesions and completely regenerated endothelium were investigated. The endothelium of rat carotid arteries was selectively damaged by laser irradiation. When [125I]LDL was injected 24 h later, the average [125I]LDL uptake in the damaged arteries was about 13 times the uptake by the non-irradiated, contralateral control arteries. Fourteen weeks after the irradiation, the vessel walls with regenerated endothelium had taken up twice as much [125I]LDL as the controls. Sixteen weeks after the irradiation, orally administered [3H]cholesterol was accumulated 5 times more by the irradiated than by the control vessel wall. These findings show that the adherent platelets contribute importantly to the LDL cholesterol accumulation by the vessel wall with acute endothelial lesion and that the regenerated endothelium promotes the accumulation of LDL cholesterol.

Endothelial damage from retrocorneal mode-locked neodymium:YAG laser pulses in monkeys

Laser pulses were focused 0.85 to 1.60 mm from the rhesus monkey corneal endothelium using a mode-locked laser at 3.3 and 4.5 mJ. Sixteen slightly off-axis pulses were applied with no contact lens on the eye. Corneal damage was studied clinically and by scanning electron microscopy. The retrocorneal distance for a 50% incidence of endothelial damage (LD 50 = lesion distance, 50%) for 3.3 mJ mode-locked pulses was found to be 1.60 mm. All mode-locked pulses of 4.5 mJ focused 0.85 to 1.60 mJ from the endothelium caused damage. In comparison, Q-switched pulses of 12 mJ or less are not likely to damage the cornea if focused more than 0.75 mm from the endothelium. The severe, early effect of mode-locked pulses is edema of endothelial cells in a 0.2- to 0.3-mm diameter circular zone surrounding a 0.1-mm diameter denuded zone with a small central break of Descemet's membrane. By two months, mild and moderate lesions heal with little or no distortion of the endothelial mosaic. Irregular enlargement of endothelial cells surrounding and covering the previously denuded area of severe lesions is caused by both mode-locked and Q-switched treatment. In no case was there clinically significant, persistent damage in the healed monkey corneas.

Prostacyclin synthesis in irradiated endothelial cells cultured from bovine aorta

Confluent monolayers of bovine aortic endothelial cells were examined 2-72 h after exposure to 0.5-5.0 Gy of 60Co gamma-rays. Accumulation of prostacyclin [PGI2, measured as 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha)] in the culture media and PGI2 production stimulated by exogenous arachidonate were correlated with cell detachment and release of lactate dehydrogenase (LDH) activity. Platelet adherence to irradiated and control monolayers also was studied. There were simultaneous time- and dose-dependent increases in cell detachment and in the titers of 6-keto-PGF1 alpha and LDH activity in the culture medium. These changes were evident between 4 and 8 h after 5 Gy or at 24 h after 0.5 Gy. Four hours after 5 Gy, both adherent and detached endothelial cells showed a twofold increase in PGI2 production during a 15-min incubation with arachidonate (10 microM). However, by 72 h this increase was less significant. The accumulation of 6-keto-PGF1 alpha appeared to be related to cell destruction, but radiation also stimulated PGI2 synthesis independent of cell detachment. There was an increased platelet interaction with irradiated monolayers, as a result of platelet adherence to subendothelial matrix exposed after cell detachment. However, irradiation did not alter the nonadherent property of the endothelial cell surface toward platelets.

Effects of 2.45-GHz microwaves on primate corneal endothelium

Both eyes of anesthetized cynomolgus monkeys (Macaca fascicularis) were irradiated with 2.45-GHz microwaves, either pulsed or continuous wave. In vivo corneal endothelial abnormalities were observed by specular microscopy and confirmed through histologic techniques after a 16- to 48-hour postexposure period. Pulsed microwaves with an average power density of 10 mW/cm2 (equivalent to a specific absorption rate (SAR) = 2.6 W/kg) produced these effects, while levels of 20-30 mW/cm2 (equivalent to a SAR = 5.3 to 7.8 W/kg) with continuous wave irradiation were required to produce similar changes.