Bone turnover change after randomized switch from tenofovir disoproxil to tenofovir alafenamide fumarate in men with HIV

OBJECTIVE

Bone loss in people with HIV (PWH) is poorly understood. Switching tenofovir disoproxil fumarate (TDF) to tenofovir alafenamide (TAF) has yielded bone mineral density (BMD) increases. PETRAM (NCT#:03405012) investigated whether BMD and bone turnover changes correlate.

DESIGN

Open-label, randomized controlled trial.

SETTING

Single-site, outpatient, secondary care.

PARTICIPANTS

Nonosteoporotic, virologically suppressed, cis-male PWH taking TDF/emtricitabine (FTC)/rilpivirine (RPV) for more than 24 weeks.

INTERVENTION

Continuing TDF/FTC/RPV versus switching to TAF/FTC/RPV (1 : 1 randomization).

MAIN OUTCOME MEASURES

:[ 18 F]NaF-PET/CT for bone turnover (standardized uptake values, SUV mean ) and dual-energy x-ray absorptiometry for lumbar spine and total hip BMD.

RESULTS

Thirty-two men, median age 51 years, 76% white, median duration TDF/FTC/RPV 49 months, were randomized between 31 August 2018 and 09 March 2020. Sixteen TAF:11 TDF were analyzed. Baseline-final scan range was 23-103 (median 55) weeks. LS-SUV mean decreased for both groups (TAF -7.9% [95% confidence interval -14.4, -1.5], TDF -5.3% [-12.1,1.5], P  = 0.57). TH-SUV mean showed minimal changes (TAF +0.3% [-12.2,12.8], TDF +2.9% [-11.1,16.9], P  = 0.77). LS-BMD changes were slightly more favorable with TAF but failed to reach significance (TAF +1.7% [0.3,3.1], TDF -0.3 [-1.8,1.2], P  = 0.06). Bone turnover markers decreased more with TAF ([CTX -35.3% [-45.7, -24.9], P1NP -17.6% [-26.2, -8.5]) than TDF (-11.6% [-28.8, +5.6] and -6.9% [-19.2, +5.4] respectively); statistical significance was only observed for CTX ( P  = 0.02, P1NP, P  = 0.17).

CONCLUSION

Contrary to our hypothesis, lumbar spine and total hip regional bone formation (SUV mean ) and BMD did not differ postswitch to TAF. However, improved LS-BMD and CTX echo other TAF-switch studies. The lack of difference in SUV mean may be due to inadequate power.

Sacroiliac pain and CT-guided steroid injection treatment: high-grade arthritis has an adverse effect on outcomes in long-term follow-up

OBJECTIVE

The sacroiliac joint (SIJ) is one of the major sources of low back pain that can lead to severe morbidity. Possible SIJ pain requires a thorough evaluation and treatment option. The purpose of this study was to analyze the possible relationships between computed tomography (CT) grading of SIJ arthritis and the effectiveness of intraarticular steroid injection treatment under CT guidance.

PATIENTS AND METHODS

A total of 61 patients with SIJ pain who were treated with CT guided intraarticular steroid injection were retrospectively reviewed. Visual analog scale (VAS) scores for pain control were recorded for short-term (day after injection, first week, third week) and long-term (sixth months and final control) follow-up times. SIJ arthritis was graded using CT images according to the New York criteria. Patients were assigned into low-grade (0, 1 and 2) and high-grade (3 and 4) groups. The relationship between arthritis grades and VAS scores in short and long-term follow-ups were statistically analyzed.

RESULTS

Mean age and follow-up was 54.8 years (range: 41-68 years) and 27.8 months (range: 24-36 months), respectively. In 40 patients there was low-grade arthritis, while 21 patients were characterized on having high-grade sacroiliac arthritis detected during the radiological evaluation. There was no statistically significant difference between low and high-grade arthritis in regard to short-term VAS scores. On contrary, for long-term VAS scores, there was significant difference between low- and high-grade arthritis.

CONCLUSIONS

Steroid injection treatment for SIJ pain is not effective on a long-term basis for patients with high-grade arthritis, and although they have had decreased VAS scores in the short-term, after 2 years of follow-up, their VAS scores significantly increased leading to symptomatic sacroiliac joint pain.

Right common iliac artery stenosis and stent insertion in Behçet's disease

Behçet's disease is a multisystem inflammatory disorder that is classified among the vasculitides and can affect all types and sizes of blood vessels. Vascular manifestations of Behçet's disease are venous and arterial occlusion, and arterial aneurysms. As vasculitis of the vasa vasorum is the main pathological hallmark of Behçet's disease, it is generally seen as superficial thrombo-phlebitis or occlusion of the major veins; however arterial obstruction and aneurysms may also be seen to a lesser extent. Iliac artery stenosis is highly uncommon. Here, a case of common iliac stenosis in a 48-year-old patient with Behçet's disease is reported. As the risk of aneurysm during an operation was high in this patient, he was treated with vascular stent implantation. Due to stent occlusion two months after the operation, percutaneous transluminal angioplasty was performed with an 8-mm balloon. During the three-year follow up, no obstruction was observed.

Diagnosing common parotid tumours with magnetic resonance imaging including diffusion-weighted imaging vs fine-needle aspiration cytology: a comparative study

OBJECTIVES

the purpose of this study was to evaluate the accuracy of MRI combined with diffusion-weighted imaging (DWI) vs fine-needle aspiration cytology (FNAC) in diagnosing common parotid masses.

METHODS

25 consecutive patients (mean age 61 years) with parotid masses were included in this study. Informed consent and ethical approval was obtained. 22 patients underwent both MRI combined with DWI and FNAC. From DWI data, apparent diffusion coefficient maps were generated. The MRI study protocol consisted of T(1) weighted spin echo; T(2) weighted and T(2) weighted fat-suppressed turbo spin echo; DWI; and T(1) weighted fat-suppressed post-contrast images. MRI and FNAC diagnoses were compared with histopathology. Youden's index was used to compare the two methods.

RESULTS

masses comprised eight Warthin tumours, eight adenomas (six pleomorphic adenomas, two basal cell adenomas), five carcinomas, two lipomas, one haemagioma and one benign lymphadenopathy. Technically, MRI was successful in 24 of the 25 patients (96%), FNAC was successful in 20 of the 23 patients (87.0%). The accuracy, sensitivity and specificity of MRI without DWI were 96%, 80% and 100%, respectively. Diagnostic accuracy did not increase by adding DWI to conventional MRI; however, DWI was helpful for diagnosing benign tumour histology. MRI combined with DWI was successful for determining accurate tumour typing in all benign masses except one lymphadenopathy. When FNAC had adequate material the accuracy, sensitivity and specificity were 95%, 75% and 100%, respectively. Youden's index was 0.80 for MRI and 0.75 for FNAC.

CONCLUSIONS

MRI combined with DWI seems to have similar diagnostic potential as FNAC in differentiation of benign vs malignant parotid masses.

A walking model to assess the onset of analgesia in osteoarthritis knee pain

OBJECTIVE

To assess a walking model utilizing a set of standardized treadmill walks to measure acute analgesic response in osteoarthritis (OA) of the knee.

DESIGN

Randomized, double-blind, placebo-controlled, multiple dose, three-period crossover study. Patients > or =45 years of age (N=22) with symptomatic knee OA were randomized to naproxen 500 mg bid, tramadol/acetaminophen 37.5 mg/325 mg in forced titration, or placebo in each of three periods. Patients performed multiple 20-minute treadmill walks on Day 1 and Day 3 at a consistent self-selected pace predetermined at screening. Pain intensity (PI) during the walks was assessed on an 11-point numerical rating scale at 0, 3, 6, 9, 12, 15, 18, and 20 min. The primary endpoint was the time-weighted average (TWA) change from baseline PI on Day 3 for the two self-paced walks for the active treatments vs placebo. Time to moderate pain (TTMP) was a key secondary endpoint.

RESULTS

Compared with placebo, the TWA change from baseline PI on Day 3 was significantly better with tramadol/acetaminophen (P=0.043) but not with naproxen (P=0.089). TWA change from baseline on Day 1 was also significantly better with both tramadol/acetaminophen (P=0.001) and naproxen (P=0.048) compared with placebo. TTMP was significantly better for tramadol/acetaminophen and naproxen than placebo (P<0.001 to P=0.015) for walks on Day 1 after a single dose and on Day 3.

CONCLUSIONS

This novel OA pain model was able to discriminate both tramadol/acetaminophen and naproxen from placebo after single and multiple doses. ClinicalTrials.gov identifier: NCT00772967.

Correction of displaced peritoneal dialysis catheters with an angular stiff rod

BACKGROUND

Fluoroscopically guided guidewire manipulations are readily available and inexpensive methods of correcting malfunctioning peritoneal dialysis catheters, with reported success rates ranging from 25% to 67%.

PURPOSE

To improve the success rates of guidewire manipulations with a modified technique.

MATERIAL AND METHODS

Using a stiff rod and a stiff wire under fluoroscopy guidance, catheters that had migrated were drawn back into the rectovesical pouch. An angular rod was used to lever the catheter downward, and the guidewire was used to push the catheter down.

RESULTS

No complications developed, and immediate success was achieved in 13 of 14 interventions. With this technique, catheter patency in chronic ambulatory peritoneal dialysis (CAPD) patients (11/12) was higher than that of previously reported methods. Durable success was maintained in nine of 12 patients after a single intervention. All re-manipulations (2/2) were successful.

CONCLUSION

Although used in only 14 interventions in 12 patients, the outcome was promising. This method is a safe and favorable alternative to other guidewire manipulations, based on absence of complications and high success.

Endovascular stent placement in patients with hepatic artery stenoses or thromboses after liver transplant

Hepatic artery stenosis or thrombosis following liver transplant is a potentially life-threatening complication. Successful liver transplant depends on uncompromised hepatic arterial inflow. Early diagnosis and treatment of complications prolong graft survival. Interventional radiologic techniques are frequently used to treat hepatic artery complications. Twenty patients with hepatic artery stenoses (n = 11) or thromboses (n = 9) were included in this study. Eighteen of the 20 patients were successfully treated by stent placement. In 9 patients, early endovascular interventions were performed 1 to 7 days after surgery. Two patients were operated owing to the effects of dissection and bleeding from the hepatic artery. Repeat endovascular interventions were performed 10 times in 6 patients. Follow-up ranged from 5 months to 4.5 years. Nine patients with patent hepatic arteries died during follow-up owing to reasons unrelated to the hepatic artery interventions. In 3 patients, the stents became occluded at 3, 5, and 9 months after surgery but no clinical symptoms were present.

Multidetector Computed Tomographic Angiography Findings of Splenic Artery Steal Syndrome in Liver Transplantation

AIMS

Splenic artery steal syndrome, a common complication in liver transplantation, is diagnosed by conventional angiography showing an enlarged splenic artery and by dynamic findings. The aim of this study was to determine multidetector computed tomographic angiography (MDCTA) findings of splenic artery steal syndrome to develop diagnostic criteria.

MATERIALS AND METHODS

Ten patients were diagnosed as displaying splenic artery steal syndrome among 198 liver transplant patients. The diagnosis was confirmed by celiac angiography. In eight of them, MDCTA was performed. Axial and coronal maximum-intensity projection images were obtained in arterial and portal phases. We measured the diameter of the celiac trunk and of the splenic, left gastric, common hepatic, superior mesenteric artery, and transplant hepatic arteries. We also measured the diameter of the proximal and the distal segments of the abdominal aorta, along with the size of the spleen, the ratio of the splenic artery to the common hepatic artery, the ratio of splenic artery to transplant hepatic artery, the diameter of portal vein and superior mesenteric vein. The control group consisted of liver transplant patients with normal liver enzyme levels. We performed Student t test for statistical examination.

RESULTS

The diameter of the splenic artery (P<.05), the size of the spleen (P<.01), and the ratio of the splenic to the transplant hepatic arteries (P<.05) was significant between the two groups. The diameter of the splenic artery was larger than 4 mm in all patients in the study group.

CONCLUSIONS

Conventional angiography was mandatory for the diagnosis of splenic artery steal syndrome. MDCTA is a noninvasive method. Some computed tomography criteria are important for early diagnosis and treatment.

Nonvascular complications in pediatric liver recipients: multidetector computed tomography evaluation

In pediatric liver transplantation postoperative diagnosis of complications is crucial for graft salvage. Multidetector computed tomography (MDCT) is a technique to evaluate complications. In this study we present nonvascular abdominal complications encountered in pediatric recipients after liver transplantation. We retrospectively examined 113 MDCT examinations in 43 pediatric patients who underwent liver transplantation between 1997 and 2005. Computed tomography (CT) examinations were made by a 16-detector multislice CT scanner. The pathological findings on CT images were: intraperitoneal free fluid, intrahepatic bile duct dilatation, graft liver infarction, perihepatic and intraperitoneal fluid collections (six biloma), colonic and/or intestinal dilatation, splenic infarction, perihepatic hematoma, right adrenal hemorrhage, perihepatic abscess, incisional hernia, intrahepatic biloma and periportal collar. In one patient intestinal hemorrhage was suspected. Intestinal perforation was suspected in three patients. Among these three patients, one patient died before any surgical intervention. In two patients the diagnosis was confirmed at surgery. In pediatric patients, the short examination time, brief sedation duration, and high-resolution images make MDCT an effective radiological method to evaluate nonvascular transplant complications.

The retinal ganglion cell layer and visual acuity of the camel

We examined the retinal ganglion cell layer of the dromedary camel, Camelus dromedarius. We have estimated that there are 8 million neurons in the ganglion cell layer of this large retina (mean area of 2,300 mm(-2)). However, only approximately 1 million are considered to be ganglion cells. The ganglion cells are arranged as two areas of high cell density, one in the temporal and one in the nasal retina. Densities of ganglion cells between these two high density regions is much lower, often less than 100 per mm(-2). In between these two high density regions, on the nasal side of the optic nerve head, is a unique and dense vertical streak of mostly non-ganglion cells; the function of this specialization is unknown. On the basis of ganglion cell density we estimate that the peak acuity in the dromedary camel is about 10 and 9.5 cycles per degree in the temporal and nasal high density regions respectively and falls to 2-3 cycles per degree in the central retina. Behavioral acuity was estimated for one bactrian camel and was found to be approximately 10 cyc deg(-1). The camel has a retina with a mean thickness of 104 microm, less than the 143 microm thickness that has previously been thought to be necessary for a retinal vasculature. Nevertheless, there is an extensive vitreal vasculature that does not appear to spare any retinal region.

Myctolaimellus robiniae n. sp. (Diplogasterida: Cylindrocorporidae) from Larval Cavities of the Locust Borer, Megacyllene robiniae Forster

A new nematode species of the family Cylindrocorporidae and the genus Myctolaimellus from subcortical cavities made by the locust borer (Megacyllene robiniae Forster) in black locust (Robinia pseudoacacia L.) is described. Males of the new species have a length of 700 to 1,050 microm; a bursate tail, peloderan with nine pairs of rays; and knobbed, curved spicules with tips bending gently into a hook. The distinctive gubernaculum is half the length of the spicules, deeply grooved longitudinally along both its dorsal and ventral surfaces, and has a spoon-shaped end. Females have a length of 830 to 1,340 microm, an amphidelphic reproductive tract with long ovaries crossing each other to extend beyond the equatorial vulva, and a gradually tapering tail.

Neuronal density in the human retinal ganglion cell layer from 16-77 years

Literature assessing whether or not neurons (retinal ganglion cells and displaced amacrine cells) are lost from the retinal ganglion cell layer in mammals with age is still controversial, some studies finding a decrease in cell density and others not. To date there have been no studies estimating the total number of neurons in the retinal ganglion cell layer of humans throughout life. Recent studies have concentrated on the macular region and examined cell densities, which are reported to decrease during aging. In a study of the human retinal pigment epithelium (RPE), we showed that, while RPE cell number does not change, cell density increases significantly in central temporal retina (macular region) as the retina ages. We speculated that the increase in density represents a "drawing together" of the retinal sheet to maintain high cell densities, in this region of the neural retina, in the face of presumed cell loss from the ganglion cell layer due to aging. Here, therefore, we have sampled the entire ganglion cell layer of the human retina and estimated total neuron numbers in 12 retinae aged from 16 to 77 years. Human retinae, fixed in formalin, were obtained from the Queensland Eye Bank and whole-mounted, ganglion cell layer uppermost. The total number of neurons was lower in the older than younger retinae and neuronal density was lower in most retinal regions in older retinae. Retinal area increased with age and neuronal density fell throughout the retina with a mean reduction of 0.53% per year. However, the percentage reduction in density was much lower for the macular region, with a value of 0.29% per year. It is possible that this lesser reduction in cell density in the macula is a result of the drawing together of the retinal sheet in this region as we speculated from RPE data.

First evidence of diversity in eutherian chiasmatic architecture: tree shrews, like marsupials, have spatially segregated crossed and uncrossed chiasmatic pathways

In the optic chiasm of mammals, axons either cross the midline to the opposite side of the brain or remain uncrossed. In the eutherian species studied to date, uncrossed axons in the caudal nerve are found in all regions. In the chiasm, they are dispersed through the hemichiasm, with many axons approaching the midline and then turning back to enter the same side of the brain as the originating eye. In marsupials, by contrast, uncrossed axons never approach the midline; instead, they remain grouped in the lateral nerve and chiasm. The impression gained from these data is that there is a major difference in chiasmatic architecture between eutherian and marsupial mammals. Therefore, the mechanisms by which axons choose their route through the chiasm was also thought to differ between the two major groups of mammals. However, the present study shows that the chiasm of a highly visual eutherian mammal, the tree shrew, is similar to that found in marsupials, with uncrossed axons confined to lateral regions and not approaching the midline. However, unlike marsupials, in the tree shrew, optic fascicles in the chiasm are often separated by thick collagen bundles. It is probable that the chiasmatic structure described to date for eutherian mammals is not ubiquitous, as was previously thought, and theories explaining the mechanisms by which axons chose their route through the chiasm during development will have to be expanded.

Spermiogenesis and spermiation in a marsupial, the tammar wallaby (Macropus eugenii)

Fourteen steps of spermatid development in the tammar wallaby (Macropus eugenii), from the newly formed spermatid to the release of the spermatozoon into the lumen of the seminiferous tubules, were recognised at the ultrastructural level using transmission and scanning electron microscopy. This study confirmed that although the main events are generally similar, the process of the differentiation of the spermatid in marsupials is notably different and relatively more complex than that in most studied eutherian mammals and birds. For example, the sperm head rotated twice in the late stage of spermiogenesis: the shape of the spermatid changed from a T-shape at step 10 into a streamlined shape in step 14, and then back to T-shape in the testicular spermatozoa. Some unique figures occurring during the spermiogenesis in other marsupial species, such as the presence of Sertoli cell spurs, the nuclear ring and the subacrosomal space, were also found in the tammar wallaby. However, an important new finding of this study was the development of the postacrosome complex (PAC), a special structure that was first evident as a line of electron dense material on the nuclear membrane of the step 7 spermatid. Subsequently it became a discontinuous line of electron particles, and migrated from the ventral side of the nucleus to the area just behind the posterior end of the acrosome, which was closely located to the sperm-egg fusion site proposed for Monodelphis domestica (Taggart et al. 1993). The PAC and its possible role in both American and Australian marsupials requires detailed examination. Distinct immature features were discovered in the wallaby testicular spermatozoa. A scoop shape of the acrosome was found on the testicular spermatozoa of the tammar wallaby, which was completely different to the compact button shape of acrosome in ejaculated spermatozoa. The fibre network found beneath the cytoplasm membrane of the midpiece of the ejaculated sperm also did not occur in the testicular spermatozoa, although the structure of the principle piece was fully formed and had no obvious morphological difference from that of the epididymal and ejaculated spermatozoa. The time frame of the formation of morphologically mature spermatozoa in the epididymis of the tammar wallaby needs to be determined by further studies.

Tropospheric ozone: respiratory effects and Australian air quality goals

OBJECTIVE

To review the health effects of tropospheric ozone and discuss the implications for public health policy.

DESIGN

Literature review and consultation with scientists in Australia and overseas. Papers in English or with English language abstracts were identified by Medline search from the international peer reviewed published reports. Those from the period 1980-93 were read systematically but selected earlier papers were also considered. Reports on ozone exposures were obtained from environmental agencies in the region.

RESULTS

Exposure to ozone at concentrations below the current Australian air quality goal (0.12 ppm averaged over one hour) may cause impaired respiratory function. Inflammatory changes in the small airways and respiratory symptoms result from moderate to heavy exercise in the presence of ozone at levels of 0.08-0.12 ppm. The changes in respiratory function due to ozone are short lived, vary with the duration of exposure, may be modified by levels of other pollutants (such as sulphur dioxide and particulates), and differ appreciably between individuals. Bronchial lavage studies indicate that inflammation and other pathological changes may occur in the airways before reductions in air flow are detectable, and persist after respiratory function has returned to normal. It is not known whether exposures to ozone at low levels (0.08-0.12 ppm) cause lasting damage to the lung or, if such damage does occur, whether it is functionally significant. At present, it is not possible to identify confidently population subgroups with heightened susceptibility to ozone. People with asthma may be more susceptible to the effects of ozone than the general population but the evidence is not consistent. Recent reports suggest that ozone increases airway reactivity on subsequent challenge with allergens and other irritants. Animal studies are consistent with the findings in human populations.

CONCLUSION

A new one hour air quality ozone goal of 0.08 ppm for Australia, and the introduction of a four hour goal of 0.06 ppm are recommended on health grounds.

Interactions of cimetidine and ranitidine with aluminum-containing antacids and a clay-containing gastric-protective drug in an "artificial stomach-duodenum" model

Interactions of cimetidine and ranitidine with aluminum-containing antacids and clay-containing gastric-protective drugs were analyzed in vitro by using an artificial stomach-duodenum model. The model reproduced near-physiologic conditions, taking into account gastric and duodenal flux variations and interactions between gastric mucosa and drugs added to the gastric content. Clay bound cimetidine in acid medium, but the drug was released when the pH increased, resulting in cimetidine amounts in the duodenal site close to those in controls. In contrast, clay bound ranitidine in acid medium and did not release it in the duodenal site. Aluminum-containing antacids did not significantly modify the amount of cimetidine or ranitidine available for absorption. Several factors play a role in the interactions of cimetidine and ranitidine with aluminum-containing antacids and clay-containing gastric-protective drugs: the structure of the antisecretory drugs, gastroduodenal pH, interactions of the antacid and clay with the gastric mucosa, and release of aluminum that could adsorb the drugs or prevent their adsorption by the mucosa. These phenomena are intricate and difficult to analyze without using a physicochemical approach.

Horizontal cells in the retina of the brush-tailed possum

Most species of eutherian (placental) mammals examined have two types of horizontal cell, one is axonless and the other has a short axon. We have recently shown that a marsupial, the quokka wallaby, also has two types of horizontal cell and that the axonless cell in this species has unusual stubby processes that pass through the inner nuclear layer to reach the inner plexiform layer. In order to discover whether these descending processes are a feature of marsupials in general, I examined the morphology of retinal horizontal cells in the brush-tailed possum, using horseradish peroxidase labelling. There are two types of horizontal cell in the possum. One type is axonless and has long, fine dendrites somewhat similar to that in the quokka; however, there are several marked differences between the axonless cells seen in the two species. The axonless cell in the possum has on average ten secondary dendrites, twice as many as seen in the quokka. These dendrites are arranged in a radial distribution, unlike those in the quokka, which are polarised in a direction often orthogonal to the overlying ganglion cell axons. Axonless horizontal cells in the possum do not have descending processes that reach the inner plexiform layer as has been seen in the quokka. The second horizontal cell type, the short-axon cell, has an axon and an axonal arbor and is similar to the short-axon cell seen in the retina of the quokka. Therefore, the morphology of the axonless horizontal cell appears to be variable, while that of the short-axon cell is conserved in marsupials as in eutherians.

Calcium and pH in anoxic and toxic injury

The critical events that lead to the transition from reversible to irreversible injury remain unclear. Studies are reviewed that have suggested that a rise in cytosolic free Ca2+ initiates plasma membrane bleb formation and a sequence of events that leads ultimately to cell death. In recent studies, we have measured changes in cytosolic free Ca2+, mitochondrial membrane potential, cytosolic pH, and cell surface blebbing in relation to the onset of irreversible injury and cell death following anoxic and toxic injury to single hepatocytes utilizing multiparameter digitized video microscopy (MDVM). MDVM is an emerging new technology that permits single living cells to be labeled with multiple probes whose fluorescence is responsive to specific cellular parameters of interest. Fluorescence images specific for each probe are collected over time, and then digitized and stored. Image analysis and processing then permits quantitation of the spatial distribution of the various parameters within the single living cells. Our results indicate the following: (1) formation of plasma membrane blebs accompanies all types of injury in hepatocytes; (2) cell death is a rapid event, initiated by rupture of a plasma membrane bleb, and is coincident with the onset of irreversible injury; (3) an increase of cytosolic free Ca2+ is not the stimulus for bleb formation or the final common pathway leading to cell death; (4) a decrease of mitochondrial membrane potential precedes loss of cell viability; (5) cytosolic pH falls by more than 1 pH unit during chemical hypoxia. This acidosis protects against the onset of cell death.