Search

Supplementary Data from Targeting PBR by Hexaminolevulinate-Mediated Photodynamic Therapy Induces Apoptosis through Translocation of Apoptosis-Inducing Factor in Human Leukemia Cells

Photodynamic therapy (PDT) with endogenous protoporphyrin IX derived from 5-aminolevulinic acid or its derivatives has been established for treatments of several premalignancies and malignancies; however, the mechanism of the modality is not fully elucidated. The mitochondrial permeability transition pore consists mainly of the mitochondrial outer membrane voltage-dependent anion channel and the peripheral benzodiazepine receptor (PBR) and the mitochondrial inner membrane adenine nucleotide translocator (ANT). These mitochondrial proteins are responsible for the permeability transition that leads to apoptosis. In the present study, the human leukemia cell line, Reh, was treated with PDT using hexaminolevulinate (HAL). More than 80% of apoptotic Reh cells were found after HAL-mediated PDT (HAL-PDT) with high-molecular-weight (50 kbp) DNA fragmentation. Addition of PK11195 or Ro5-4864, two ligands of PBR, during HAL-PDT significantly inhibited the apoptotic effect. Bongkrekic acid, a ligand for ANT, also reduced the PDT effect. Although the mitochondrial transmembrane potential collapsed, neither cytosolic translocation of mitochondrial cytochrome c nor activation of caspase-9, caspase-8, caspase-3, and poly(ADP-ribose) polymerase were found. However, nuclear translocation of mitochondrial apoptosis-inducing factor (AIF) was shown by both immunoblotting and immunocytochemistry. Because AIF is the sole one among all proapoptotic factors involved in caspase-dependent and caspase-independent pathways that induces the high-molecular-weight DNA fragmentation, we conclude that HAL-PDT specifically targets PBR, leading to apoptosis of the Reh cells through nuclear translocation of mitochondrial AIF. This study suggests PBR as a possible novel therapeutic target for HAL-based PDT of cancer.

This interpretivist community participatory study explores carers’ beliefs about the potential usefulness of counselling in relation to the caring role. Twenty semi-structured interviews with carers were transcribed and analysed thematically. All participants thought counselling could potentially be helpful to carers, but their ideas about the ways in which it would help varied according to whether or not they had personal experience of counselling. Only carers with counselling experience had an awareness of counselling as focussing on changing feelings, thoughts, attitudes and behaviours. The implications of the findings for the provision of counselling services are discussed.

Cardiovascular disease is more common in patients with chronic kidney disease (CKD), and traditional risk factors do not adequately predict those at risk for cardiovascular (CV) events. Recent evidence suggests elevated trimethylamine N-oxide (TMAO), created by gut microflora from dietary L-carnitine and choline, is associated with CV events. We investigated the relationship of TMAO levels in patients with stages 3b and 4 CKD to ischemic CV events using the CanPREDDICT cohort, a Canada-wide observational study with prospective 3-year follow-up of adjudicated CV events. Baseline samples were obtained for 2529 CKD patients. TMAO, choline, and L-carnitine levels were measured using tandem mass spectrometry. Baseline median TMAO level was high for the whole cohort (20.41 μM; interquartile range [IQR]: 12.82–32.70 μM). TMAO was independently associated with CV events (hazard ratio 1.23; 95% confidence interval: 1.06–1.42 / 1 SD lnTMAO) after adjusting for all potential CV risk factors. Those in the highest TMAO quartile had significantly higher risk of CV events (adjusted hazard ratio 1.59; 95% confidence interval: 1.04–2.43; P = 0.0351) in the analysis of recurring ischemic events. Among those with stage 3b CKD (hazard ratio 1.45; 95% confidence interval: 1.12–1.87 / 1 SD lnTMAO), independent of kidney function, TMAO levels identified those at highest risk for events. Our results suggest that TMAO may represent a new potentially modifiable CV risk factor for CKD patients. Further studies are needed to determine sources of variability and if lowering of TMAO reduces CV risk in CKD.

We examined a series of selenorhodamines with amide and thioamide functionality at the 5-position of a 9-(2-thienyl) substituent on the selenorhodamine core for their potential as photosensitizers for photodynamic therapy (PDT) in P-glycoprotein (P-gp) expressing cells. These compounds were examined for their photophysical properties (absorption, fluorescence, and ability to generate singlet oxygen), for their uptake into Colo-26 cells in the absence or presence of verapamil, for their dark and phototoxicity toward Colo-26 cells, for their rates of transport in monolayers of multidrug-resistant, P-gp-overexpressing MDCKII-MDR1 cells, and for their colocalization with mitochondrial specific agents in Colo-26 cells. Thioamide derivatives 16b and 18b were more effective photosensitizers than amide derivatives 15b and 17b. Selenorhodamine thioamides 16b and 18b were useful in a combination therapy to treat Colo-26 cells in vitro: a synergistic therapeutic effect was observed when Colo-26 cells were exposed to PDT and treatment with the cancer drug doxorubicin.

Rationale and Objectives The treatment of nonmelanoma skin cancer (NMSC) is usually by surgical excision or Mohs micrographic surgery and alternatively may include photodynamic therapy (PDT). To guide surgery and to optimize PDT, information about the tumor structure, optical parameters, and vasculature is desired. Materials and Methods Spatial frequency domain imaging (SFDI) can map optical absorption, scattering, and fluorescence parameters that can enhance tumor contrast and quantify light and photosensitizer dose. High frequency ultrasound (HFUS) imaging can provide high-resolution tumor structure and depth, which is useful for both surgery and PDT planning. Results Here, we present preliminary results from our recently developed clinical instrument for patients with NMSC. We quantified optical absorption and scattering, blood oxygen saturation (StO 2 ), and total hemoglobin concentration (THC) with SFDI and lesion thickness with ultrasound. These results were compared to histological thickness of excised tumor sections. Conclusions SFDI quantified optical parameters with high precision, and multiwavelength analysis enabled 2D mappings of tissue StO 2 and THC. HFUS quantified tumor thickness that correlated well with histology. The results demonstrate the feasibility of the instrument for noninvasive mapping of optical, physiological, and ultrasound contrasts in human skin tumors for surgery guidance and therapy planning.

5-aminolaevulinic acid photodynamic therapy (ALA-PDT) is an attractive treatment option for nonmelanoma skin tumors, especially for multiple lesions and large areas. The efficacy of ALA-PDT is highly dependent on the photosensitizer (PS) concentration present in the tumor. Thus it is desirable to quantify PS concentration and distribution, preferably noninvasively to determine potential outcome. Here we quantified protoporphyrin IX (PpIX) distribution induced by topical and intra-tumoral (it) administration of the prodrug ALA in basal and squamous cell carcinoma murine models by using spatial frequency domain imaging (SFDI). The in vivo measurements were validated by analysis of the ex vivo extraction of PpIX. The study demonstrates the feasibility of non-invasive quantification of PpIX distributions in skin tumors.

We report a novel post-loading approach for constructing a multifunctional biodegradable polyacrylamide (PAA) nanoplatform for tumor-imaging (fluorescence) and photodynamic therapy (PDT). This approach provides an opportunity to post-load the imaging and therapeutic agents at desired concentrations. Among the PAA nanoparticles, a formulation containing the photosensitizer, HPPH [3-(1’-hexyloxyethyl)pyropheophorbide-a], and the cyanine dye in a ratio of 2:1 minimized the undesirable quenching of the HPPH electronic excitation energy due to energy migration within the nanoparticles and/or Förster (fluorescence) resonance energy transfer (FRET) between HPPH and cyanine dye. An excellent tumor-imaging (NIR fluorescence) and phototherapeutic efficacy of the nanoconstruct formulation is demonstrated. Under similar treatment parameters the HPPH in 1% Tween 80/5% aqueous dextrose formulation was less effective than the nanoconstruct containing HPPH and cyanine dye in a ratio of 2 to 1. This is the first example showing the utility of the post-loading approach in developing a nanoconstructs for tumor-imaging and therapy.

Objective: A hydrophobic photosensitizer, 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH), was loaded into nontoxic biodegradable amine functionalized polyacrylamide (AFPAA) nanoparticles using three different methods (encapsulation, conjugation, and post-loading), forming a stable aqueous dispersion. Each formulation was characterized for physicochemical properties as well as for photodynamic performance so as to determine the most effective nanocarrier formulation containing HPPH for photodynamic therapy (PDT). Materials and Methods: HPPH or HPPH-linked acrylamide was added into monomer mixture and polymerized in a microemulsion for encapsulation and conjugation, respectively. For post-loading, HPPH was added to an aqueous suspension of pre-formed nanoparticles. Those nanoparticles were tested for optical characteristics, dye loading, dye leaching, particle size, singlet oxygen production, dark toxicity, in vitro photodynamic cell killing, whole body fluorescence imaging and in vivo PDT. Results: HPPH was successfully encapsulated, conjugated or post-loaded into the AFPAA nanoparticles. The resultant nanoparticles were spherical with a mean diameter of 29 � 3 nm. The HPPH remained intact after entrapment and the HPPH leaching out of nanoparticles was negligible for all three formulations. The highest singlet oxygen production was achieved by the postloaded formulation, which caused the highest phototoxicity in in vitro assays. No dark toxicity was observed. Post-loaded HPPH AFPAA nanoparticles were localized to tumors in a mouse colon carcinoma model, enabling fluorescence imaging, and producing a similar photodynamic tumor response to that of free HPPH in equivalent dose. Conclusions: Post-loading is the promising method for loading nanoparticles with hydrophobic photosensitizers to achieve effective in vitro and in vivo PDT. Lasers Surg. Med. 43:686–695, 2011. 2011 Wiley-Liss, Inc.

The tumor-vascular disrupting agent (VDA) vadimezan (5,6-dimethylxanthenone-4-acetic acid, DMXAA) has been shown to potentiate the antitumor activity of photodynamic therapy (PDT) using systemically administered photosensitizers. Here, we characterized the response of subcutaneous syngeneic Colon26 murine colon adenocarcinoma tumors to PDT using the locally applied photosensitizer precursor aminolevulinic acid (ALA) in combination with a topical formulation of vadimezan. Diffuse correlation spectroscopy (DCS), a non-invasive method for monitoring blood flow, was utilized to determine tumor vascular response to treatment. Additionally, correlative CD31-immunohistochemistry to visualize endothelial damage, ELISA assays to measure induction of tumor necrosis factor-alpha (TNF-α) and tumor weight measurements were also examined in separate animals. In our previous work, DCS revealed a selective decrease in tumor blood flow over time following topical vadimezan. ALA-PDT treatment also induced a decrease in tumor blood flow. The onset of blood flow reduction was rapid in tumors treated with both ALA-PDT and vadimezan. CD31-immunostaining of tumor sections confirmed vascular damage following topical application of vadimezan. Tumor weight measurements revealed enhanced tumor growth inhibition with combination treatment compared to ALA-PDT or vadimezan treatment alone. In conclusion, vadimezan as a topical agent enhances treatment efficacy when combined with ALA-PDT. This combination could be useful in clinical applications.

To investigate the effect of hydrophobicity, charge and size of photosensitizers (PS) on their encapsulation efficiency in organically modified silica nanoparticles (ORMOSIL), a series of alkyl ether analogs of 2-(1′-hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH) containing varied number of carbon units, HPPH with anionic and cationic functionalities, and HPPH analogs with molecular weight ranging from ~630 to 6000 Daltons were synthesized. Our preliminary results suggest that these factors play a significant role in encapsulation of the photosensitizers and their release from ORMOSIL nanoparticles. The synthesis and characterization of PS-encapsulated ORMOSIL and a comparative study on the effect of PS size, lipophilicity and charge on encapsulation efficiency, photophysical characteristics and release kinetics are discussed.

To develop novel bifunctional agents for tumor imaging (MR) and photodynamic therapy (PDT) certain tumor-avid photosensitizers derived from chlorophyll-a were conjugated with variable number of Gd(III)aminobenzyl DTPA moieties. All the conjugates containing three or six gadolinium units showed significant T1 and T2 relaxivities. However, as a bifunctional agent, the 3-(1′-hexyloxyethyl)pyropheophorbide-a (HPPH) containing 3Gd(III) aminophenyl DTPA was most promising with possible applications in tumor-imaging and PDT. Compared to HPPH, the corresponding 3- and 6Gd(III)aminobenzyl DTPA conjugates exhibited similar electronic absorption characteristics with a slightly decreased intensity of the absorption band at 660 nm. However, compared to HPPH, the excitation of the broad “Soret” band (near 400 nm) of the corresponding 3Gd(III)aminobenzyl-DTPA analogs showed a significant decrease in the fluorescence intensity at 667 nm, which was further diminished by increasing the number of Gd(III)units.

The carbohydrate moieties on conjugating with 3-(1′-hexyloxyethyl)-3-devinyl pyropeophorbide-a (HPPH) altered the uptake and intracellular localization from mitochondria to lysosomes. In vitro, HPPH-Gal 9 PDT showed increased PDT efficacy over HPPH–PDT as detectable by the oxidative cross-linking of nonphosphorylated STAT3 and cell killing in ABCG2-expressing RIF cells but not in ABCG2-negative Colon26 cells. This increased efficacy in RIF cells could at least partially be attributed to increased cellular accumulation of 9, suggesting a role of the ABCG2 transporter for which HPPH is a substrate. While such differences in the accumulation in HPPH derivatives by tumor tissue in vivo were not detectable, 9 still showed an elevated light dose-dependent activity compared to HPPH in mice bearing RIF as well as Colon26 tumors. Further optimization of the carbohydrate conjugates at variable treatment parameters in vivo is currently underway.

Aims: Microglia are involved in neurodegeneration, are prime targets for anti-inflammatory therapy and are potential biomarkers of disease progression. For example, positron emission tomography imaging employing radioligands for the mitochondrial translocator protein of 18 kDa (TSPO, formerly known as the peripheral benzodiazepine receptor) is being scrutinized to detect neuroinflammation in various diseases. TSPO is presumably present in activated microglia, but may be present in other neural cells. Methods: We sought to elucidate the protein expression in normal human central nervous system, several neurological diseases (HIV encephalitis, Alzheimer's disease, multiple sclerosis and stroke) and simian immunodeficiency virus encephalitis by performing immunohistochemistry with two anti-TSPO antibodies. Results: Although the overall parenchymal staining was minimal in normal brain, endothelial and smooth muscle cells, subpial glia, intravascular monocytes and ependymal cells were TSPO-positive. In disease states, elevated TSPO was present in parenchymal microglia, macrophages and some hypertrophic astrocytes, but the distribution of TSPO varied depending on the disease, disease stage and proximity to the lesion or relation to infection. Staining with the two antibodies correlated well in white matter, but one antibody also stained cortical neurones. Quantitative analysis demonstrated a significant increase in TSPO in the white matter of HIV encephalitis compared with brains without encephalitis. TSPO expression was also increased in simian immunodeficiency virus encephalitis. Conclusions: This report provides the first comprehensive immunohistochemical analysis of the expression of TSPO. The results are useful for informing the usage of positron emission tomography as an imaging modality and have an impact on the potential use of TSPO as an anti-inflammatory pharmacological target.

In situ conversion of bacteriochlorophyll-a, present in Rhodobacter sphaeroides (Rb. sphaeroides) gave bacteriopurpurin-18 in modest yield, which in a sequence of reactions was converted into two series of bacteriochlorins: bacteriopurpurinimide and bacteriopurpurin p6 with and without a fused imide ring system, respectively. To determine the effect of overall lipophilicity in photosensitizing efficacy, these bacteriochlorins were independently reacted with HBr gas and subsequently treated with various alkyl alcohols to afford the corresponding alkyl ether derivatives as diastereomeric mixtures (the R- and S-isomers were obtained in almost equal ratios). Between the two series of bacteriochlorins, the bacteriopurpurinimides containing a fused imide ring system were found to be more effective in vivo (C3H mice bearing RIF tumors). To investigate the effect of the presence of the chiral center at position 3 of the most effective purpurinimide 9 [3(1'-heptyloxy)ethyl-3-deacetyl-bacteriopurpurin-18-N-hexylimide propyl ester], the acetyl group was replaced with a hydroxymethyl substituent and converted into 3(1'-decyloxy)methyl-3-deacetyl-purpurin-18-N-hexylimide methyl ester 26 with a similar lipophilicity. Interestingly, compared to 26, the bacteriopurpurinimide 9 was found to be more effective, suggesting that the chiral center at position 3 certainly plays an important role in photosensitizing activity. Among a series of alkyl ether analogues, between the PDT efficacy and the lipophilicity (log P and log D) calculated by computational methods (PALLAS program), a parabolic relationship was observed to some extent. However, it was limited to a particular series, e.g., compounds with similar log P values between bacteriopurpurinimides and bacteriochlorin e6 did not produce similar in vivo efficacy. As expected, within a series, a linear relationship was observed between the log P values and the HPLC retention times of the photosensitizers. Some of the mitochondrial localized photosensitizers showed a significant peripheral benzodiazepine binding (PBR) affinity. However, limited correlation between PBR binding affinity and in vivo PDT efficacy was observed. Compared to the naturally occurring bacteriochlorophyll-a, the bacteriopurpurinimides with fused imide ring system showed higher in vitro/in vivo stability. In contrast to methyl pyropheophorbide-a, the ester functionalities in bacteriopurpurinimide did not convert into the corresponding carboxylic acid by the enzyme esterases.

A lactose moiety was regioselectively introduced at various positions of N-hexyl-mesopurpurinimide (a class of chlorin containing a fused six-membered imide ring system, lambda(max): 700 nm) to investigate the effect of its presence and position on photosensitizing efficacy. The resulting novel structures produced a significant difference in in vitro and in vivo efficacy. Among the positional isomers in which the lactose moiety was introduced at positions 3, 8, and 12, the 3-lactose purpurin-18-N-hexylimide produced the best efficacy. Compared to these analogues, the lactose moiety joined with an amide bond at position 17(2), and with an N-benzyl group bearing a -C[triple bond]C- linkage at position 13(2) showed reduced in vitro/in vivo photosensitivity. A noticeable difference between lactose conjugates in cell uptake (RIF tumor cells) was observed at 3 and 24 h postincubation. Replacing the lactose (Galbeta1 --> 4Glc) with beta-galactose and glucose moieties at position 3 of purpurinimide produced an increase in both cell uptake and in in vitro efficacy, but with reduced in vivo efficacy. Sites of intracellular localization differed among photosensitizers with and without carbohydrate moieties. Molecular modeling shows favorable interactions of 3- and 12-lactose-purpurinimide analogues with both galectin-1 and galectin-3, but clear contributions were not found for the conjugate containing lactose moiety at position 8. In a comparative ELISA study of the lactose conjugates with free lactose, all carbohydrate-purpurinimides showed binding to both galectins with a significant variation between the batches of galectins.

Photodynamic therapy (PDT) with endogenous protoporphyrin IX derived from 5-aminolevulinic acid or its derivatives has been established for treatments of several premalignancies and malignancies; however, the mechanism of the modality is not fully elucidated. The mitochondrial permeability transition pore consists mainly of the mitochondrial outer membrane voltage-dependent anion channel and the peripheral benzodiazepine receptor (PBR) and the mitochondrial inner membrane adenine nucleotide translocator (ANT). These mitochondrial proteins are responsible for the permeability transition that leads to apoptosis. In the present study, the human leukemia cell line, Reh, was treated with PDT using hexaminolevulinate (HAL). More than 80% of apoptotic Reh cells were found after HAL-mediated PDT (HAL-PDT) with high-molecular-weight (50 kbp) DNA fragmentation. Addition of PK11195 or Ro5-4864, two ligands of PBR, during HAL-PDT significantly inhibited the apoptotic effect. Bongkrekic acid, a ligand for ANT, also reduced the PDT effect. Although the mitochondrial transmembrane potential collapsed, neither cytosolic translocation of mitochondrial cytochrome c nor activation of caspase-9, caspase-8, caspase-3, and poly(ADP-ribose) polymerase were found. However, nuclear translocation of mitochondrial apoptosis-inducing factor (AIF) was shown by both immunoblotting and immunocytochemistry. Because AIF is the sole one among all proapoptotic factors involved in caspase-dependent and caspase-independent pathways that induces the high-molecular-weight DNA fragmentation, we conclude that HAL-PDT specifically targets PBR, leading to apoptosis of the Reh cells through nuclear translocation of mitochondrial AIF. This study suggests PBR as a possible novel therapeutic target for HAL-based PDT of cancer.

Optical imaging has attracted a great attention for studying molecular recognitions because minute fluorescent tracers can be detected in homogeneous and heterogeneous media with existing laboratory instruments. In our preliminary study, a clinically relevant photosensitizer (HPPH, a chlorophyll-a analog) was linked with a cyanine dye (with required photophysical characteristics but limited tumor selectivity), and the resulting conjugate was found to be an efficient tumor imaging (fluorescence imaging) and photosensitizing agent. Compared to HPPH, the presence of the cyanine dye moiety in the conjugate produced a significantly higher uptake in tumor than skin. At a therapeutic/imaging dose, the conjugate did not show any significant skin phototoxicity, a major drawback associated with most of the porphyrin-based photosensitizers. These results suggest that tumor-avid porphyrin-based compounds can be used as "vehicles" to deliver the desired fluorescent agent(s) to tumor. The development of tumor imaging or improved photodynamic therapy agent(s) by itself represents an important step, but a dual function agent (fluorescence imaging and photodynamic therapy) provides the potential for tumor detection and targeted photodynamic therapy, combining two modalities into a single cost-effective "see and treat" approach.

This study was designed to assess impressions of employed mothers and fathers who do not provide the primary child care in their familial context. Participants read a story about an employed mother or father who demonstrated very little direct involvement in the care of his or her child. As hypothesized, impressions of a mother who did not play a central role in care giving were more affected by whether or not she had a clear situational reason for not providing care (i.e., she was out of town) than impressions of a father. These findings imply continuing differences in child care expectations for mothers and fathers.

This experiment examined correspondence bias associated with the expression of pro- or anti-American sentiment in the months following September 11, 2001. Participants read a pro- or anti-United States essay written by a person whose name was varied to suggest that he either was or was not a Muslim. Participants were informed either that the position taken in the essay had been chosen or assigned. Inferences made about the essay writer's true opinions demonstrated strong and consistent correspondence bias only when participants believed the essay writer was not a Muslim. When participants believed the essay writer was a Muslim, correspondence bias was diminished on one measure and disappeared completely on another. These findings are consistent with the notion that participants were concerned about rushing to incorrect conclusions about a Muslim target person. The strong correspondence bias exhibited by participants making judgments about a non-Muslim is consistent with Gilbert and Malone's (1995) assertion that unrealistic expectations lead to correspondence bias.

The isomerically pure 3-deacetyl-3-(1-heptyloxy)ethylbacteriopurpurin-N-hexylimides exhibiting long-wavelength absorption near 800 nm were obtained from 3-acetylbacteriopurpurin-N-hexylimide in high stereospecificity by following Corey's synthetic approach. Both heptyl ether derivatives (R- and S-isomers) showed similar in vitro photosensitizing efficacy and limited skin phototoxicity and were found to localize in mitochondria. However, in preliminary in vivo screening, compared to the S-isomer, the corresponding R-isomer produced enhanced in vivo photodynamic therapy efficacy.

An adherence method was developed that enriches for antigen presenting cells (dendritic cells, monocytes/macrophages, and B lymphocytes) from peripheral blood mononuclear cell (PBMC) preparations. This method utilizes the cells' natural adherence to polystyrene tissue culture dishes and their subsequent removal with K3EDTA after incubation at 4 degrees, with gentle pipeting. Flow cytometric analysis revealed that on average, the enrichment of CD83+ dendritic cells, CD14+ monocytes/ macrophages, and CD19+ B cells increased by 12.5 to 20, 2, and 4 fold, respectively, compared to their initial numbers present in PBMC preparations. Cell viability, determined by trypan blue exclusion, was between 90 and 98%. After the enrichment procedure, the cells could still be activated by tetanus toxoid and this was shown by flow cytometric analysis, as enhancement of class II major histocompatibility complex (MHC) (31% increase) (after antigen treatment). This is a fast and economical alternative to other established methods for the preparation of pure, functionally competent antigen presenting cells derived from peripheral blood.

Effect of hemoglobin levels in hemodialysis patients with asymptomatic cardiomyopathy. Background Hemoglobin levels below 10 g/dL lead to left ventricular (LV) hypertrophy, LV dilation, a lower quality of life, higher cardiac morbidity, and a higher mortality rate in end-stage renal disease. The benefits and risks of normalizing hemoglobin levels in hemodialysis patients without symptomatic cardiac disease are unknown. Methods One hundred forty-six hemodialysis patients with either concentric LV hypertrophy or LV dilation were randomly assigned to receive doses of epoetin α designed to achieve hemoglobin levels of 10 or 13.5 g/dL. The study duration was 48 weeks. The primary outcomes were the change in LV mass index in those with concentric LV hypertrophy and the change in cavity volume index in those with LV dilation. Results In patients with concentric LV hypertrophy, the changes in LV mass index were similar in the normal and low target hemoglobin groups. The changes in cavity volume index were similar in both targets in the LV dilation group. Treatment-received analysis of the concentric LV hypertrophy group showed no correlation between the change in mass index and a correlation between the change in LV volume index and mean hemoglobin level achieved (8 mL/m 2 per 1 g/dL hemoglobin decrement, P = 0.009). Mean hemoglobin levels and the changes in LV mass and cavity volume index were not correlated in patients with LV dilation. Normalization of hemoglobin led to improvements in fatigue ( P = 0.009), depression ( P = 0.02), and relationships ( P = 0.004). Conclusions Normalization of hemoglobin does not lead to regression of established concentric LV hypertrophy or LV dilation. It may, however, prevent the development of LV dilation, and it leads to improved quality of life.

Comparative mortality of hemodialysis and peritoneal dialysis in Canada. Background Comparisons of mortality rates in patients on hemodialysis versus those on peritoneal dialysis have been inconsistent. We hypothesized that comorbidity has an important effect on differential survival in these two groups of patients. Methods Eight hundred twenty-two consecutive patients at 11 Canadian institutions with irreversible renal failure had an extensive assessment of comorbid illness collected prospectively, immediately prior to starting dialysis therapy. The cohort was assembled between March 1993 and November 1994; vital status was ascertained as of January 1, 1998. Results The mean follow-up was 24 months. Thirty-four percent of patients at baseline, 50% at three months, and 51% at six months used peritoneal dialysis. Values for a previously validated comorbidity score were higher for patients on hemodialysis at baseline (4.0 vs. 3.1, P P = 0.001), and six months (3.6 vs. 3.2, P = 0.005). The overall mortality was 41%. The unadjusted peritoneal dialysis/hemodialysis mortality hazard ratios were 0.65 (95% CI, 0.51 to 0.83, P = 0.0005), 0.84 (95% CI, 0.66 to 1.06, P = NS), and 0.83 (95% CI, 0.64 to 1.08, P = NS) based on the modality of dialysis in use at baseline, three months, and six months, respectively. When adjusted for age, sex, diabetes, cardiac failure, myocardial infarction, peripheral vascular disease, malignancy, and acuity of renal failure, the corresponding hazard ratios were 0.79 (95% CI, 0.62 to 1.01, P = NS), 1.00 (95% CI, 0.78 to 1.28, P = NS), and 0.95 (95% CI, 0.73 to 1.24, P = NS). Adjustment for a previously validated comorbidity score resulted in hazard ratios of 0.74 (95% CI, 0.58 to 0.94, P = 0.01), 0.94 (95% CI, 0.74 to 1.19, P = NS), and 0.88 (95% CI, 0.68 to 1.13, P = NS) at baseline, three months, and six months. There was no survival advantage for either modality in any of the major subgroups defined by age, sex, or diabetic status. Conclusions The apparent survival advantage of peritoneal dialysis in Canada is due to lower comorbidity and a lower burden of acute onset end-stage renal disease at the inception of dialysis therapy. Hemodialysis and peritoneal dialysis, as practiced in Canada in the 1990s, are associated with similar overall survival rates.

Protoporphyrin IX (PpIX), an endogenously synthesized photosensitizer, can transiently accumulate in activated lymphocytes following administration of the heme precursor 5-aminolevulinic acid (ALA). One possible mechanism of this in lymphocyte accumulation is that actively dividing cells use intracellular iron stores for cytochrome and DNA synthesis and thus do not inactivate PpIX, the photoactive precursor of heme, by iron incorporation. This selective accumulation in activated cells should allow targeting by photodynamic therapy (PDT). To determine the effect of this accumulation, we studied PDT effects on the in vitro correlate of transplantation rejection: the one-way mixed lymphocyte reaction (MLR). Selective phototoxicity was determined by photoirradiating ALAtreated, MLR-activated cells and measuring subsequent stimulation either in a secondary MLR or with phytohemagglutinin (PHA). We found that proliferation of MLR-activated lymphocytes incubated with ALA and treated with light was only 12-20% of controls (ALA+, no light) after rechallenge with the stimulator cells (P < 0.05), although their response to nonspecific PHA stimulation was similar to controls. Thus alloantigen-specific depletion was shown. The data suggest a role for ALAPDT in the treatment of diseases that require the selective elimination of activated lymphocytes and possibly as an immunomodulator.

Lymphocytes treated with delta-aminolevulinic acid (ALA) can accumulate the photoactive, fluorescent heme precursor, protoporphyrin IX (PpIX). With visible light illumination, PpIX can be used in photodynamic therapy (ALA-PDT) to kill or functionally alter cells. The aim of this study was to characterize the effects of ALA and ALA-PDT on resting and activated human peripheral blood T lymphocytes. Accumulation of PpIX depends inversely on the rate of its iron-dependent conversion into heme. Activated replicating lymphocytes have low intracellular iron levels, with corresponding increases in the transferrin receptor (CD71). Thus, we expected activated lymphocytes would preferentially accumulate PpIX. Using four-color flow cytometry, we examined ALA-induced PpIX levels in T-cell subsets of resting and activated human peripheral blood mononuclear cells and the relationship between CD71 and PpIX. Peripheral blood mononuclear cells stimulated by phytohemagglutinin (PHA) were simultaneously phenotyped for PpIX, CD71 and the T-cell markers CD3 and CD4 or CD8. In activated cells treated with 0-6 mM ALA for 4 h, PpIX fluorescence was maximal at 1 mM ALA. On a single cell basis, there was a strong correlation between PpIX accumulation and CD71 expression. The ALA-treated, PHA-stimulated, CD71+ lymphocytes had an eight-fold greater mean PpIX fluorescence than nonactivated, CD71- cells. Approximately 87% of the CD4+ and 85% of the CD8+ T cells accumulated PpIX. The PpIX levels of CD8+ cells were about 5% greater than CD4+ cells. In addition, mixed lymphocyte reaction-stimulated cells treated with ALA accumulated more PpIX than controls. Thus, activated cells preferentially accumulate endogenous PpIX when exogenous ALA is administered. Cytotoxicity studies showed that the majority of the activated cells following ALA-PDT were killed but resting cells were spared. Also, in examining activation markers by flow cytometry the number of cells that were positive for activation markers CD38 or CD71 dramatically decreased after ALA and light treatment in activated populations. The data suggest a role for ALA-PDT as an immunomodulator or photocytotoxic agent targeting activated lymphocytes.

The current experiment was designed to examineimpressions of persons who would be parents in the nearfuture and who would be in a breadwinning or exclusivelycaregiving role. Participants, who were students from a private college with a primarily whitestudent body, read a brief description of a targetperson expecting the arrival of a child. The targetperson anticipated either being employed or staying at home to care for the baby. Future employmentstatus was described as being either freely chosen ornot freely chosen. Impressions were consistent withEagly's (1987) social role theory of gender differences in social behavior and with researchdemonstrating the fundamental attribution error (Ross,1977). Participants rated persons who expected to stayat home with their child as being more communal and less agentic than persons who expected to beemployed, even when employment status was not freelychosen. Male participants gave higher approval ratingsto females who expected to stay at home with theirchildren, and female participants gave higher approvalratings to males who expected to stay at home with theirchildren.

To guide intervention planning of nonmelanoma skin cancer (NMSC), the tumor thickness and functional contrast is desired. The results indicate multimodal imaging can provide accurate structural and enhanced contrasts in NMSC.

The current experiment was designed to examine perceptions of employed and unemployed mothers and fathers in the context of Eagly's [(1987) Sex Differences in Social Behavior: A Social-Role Interpretation, Hillsdale, NJ: Erlbaum] social role theory of sex differences in social behavior. Participants, who were students from a private college with a primarily white student body, read a brief description of a mother or father who was employed or had given up employment in order to stay at home with a young child. Reasons for current or previous employment were either financial or for personal fulfillment. As predicted by Eagly's social role theory, participants rated employed mothers and fathers similarly and perceived them to be more agentic and less communal than unemployed mothers and fathers. Approval ratings deteriorated significantly when a father sacrificed financial security for care giving; the same behavior by mothers received high approval. These findings provided evidence of a continuing societal mandate for fathers (and not mothers) to provide financially for their families.

PDT has become a treatment of choice especially for the cases with multiple sites and large areas. However, the efficacy of PDT is limited for thicker and deeper tumors. Depth and size information as well as vascularity can provide useful information to clinicians for planning and evaluating PDT. High-resolution ultrasound and photoacoustic imaging can provide information regarding skin structure and vascularity. We utilized combined ultrasound-photoacoustic microscopy for imaging a basal cell carcinoma (BCC) tumor pre-PDT and the results indicate that combined ultrasound-photoacoustic imaging can be useful tool for PDT planning by providing both structural and functional contrasts.

Photodynamic Therapy (PDT) has proven to be an effective treatment option for nonmelanoma skin cancers. The ability to quantify the concentration of drug in the treated area is crucial for effective treatment planning as well as predicting outcomes. We utilized spatial frequency domain imaging for quantifying the accurate concentration of protoporphyrin IX (PpIX) in phantoms and in vivo . We correct fluorescence against the effects of native tissue absorption and scattering parameters. First we quantified the absorption and scattering of the tissue non-invasively. Then, we corrected raw fluorescence signal by compensating for optical properties to get the absolute drug concentration. After phantom experiments, we used basal cell carcinoma (BCC) model in Gli mice to determine optical properties and drug concentration in vivo at pre-PDT.

There is a need to improve the selectivity of photodynamic therapy and for better targeting of tumor cells within specific tumor compartments. Selective in vitro phototoxicity of a human bladder carcinoma cell line 647V has been achieved by targeting sulfonated aluminum phthalocyanines (AlSPc) with monoclonal antibodies. Aluminum tetra-3 sulfonyl chloride phthalocyanine (PC) or rhodamine sulfonyl chloride were directly coupled to antibodies by a sulfonamide linkage and AlSPc or carboxyfluorescein were encapsulated in liposomes of the small unilamellar vesicle type (SUV) bearing antibody. Antibody E7 (IgM subclass), which recognized an antigenic determinant expressed on 647V but was absent on T24 a control human bladder carcinoma cell line, and a control IgM antibody were used. The effects of the two types of conjugate were compared. Immunofluorescence studies on living cells demonstrated specific cell surface localization of conjugates at 4 degrees C and internalization at 37 degrees C. Phototoxicity was measured by 3-(4,5-dimethylthiazol-2-5-diphenyltetrazolium) bromide assay after exposing AlSPc-sensitized cells to red light. Significant AlSPc dose-dependent phototoxicity of the order 4 degrees C < 4 degrees C plus 37 degrees C < 37 degrees C was observed with E7-SUV and E7-PC in the range 1-8 microM AlSPc. At equimolar AlSPc doses absolute toxicity was similar for the two conjugate types, but at equimolar antibody doses, the liposomal conjugate was more effective by up to 13-fold. Addition of urine during illumination decreased toxicity, which was attributed to the presence of protective elements. The results suggest that photosensitizers such as AlSPc could be used for antibody-directed therapy and in particular for selectively damaging tumor cells of the epithelial cell compartment in bladder carcinoma by intrabladder administration. The therapeutic ratio, which takes into account both specific and nonspecific toxicity, was greater for the liposome conjugate than for the direct conjugate indicating their greater suitability for in vivo instillation.

A hydrophobic photosensitizer, 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH), was loaded into nontoxic biodegradable amine functionalized polyacrylamide (AFPAA) nanoparticles using three different methods (encapsulation, conjugation, and post-loading), forming a stable aqueous dispersion. Each formulation was characterized for physicochemical properties as well as for photodynamic performance so as to determine the most effective nanocarrier formulation containing HPPH for photodynamic therapy (PDT).HPPH or HPPH-linked acrylamide was added into monomer mixture and polymerized in a microemulsion for encapsulation and conjugation, respectively. For post-loading, HPPH was added to an aqueous suspension of pre-formed nanoparticles. Those nanoparticles were tested for optical characteristics, dye loading, dye leaching, particle size, singlet oxygen production, dark toxicity, in vitro photodynamic cell killing, whole body fluorescence imaging and in vivo PDT.HPPH was successfully encapsulated, conjugated or post-loaded into the AFPAA nanoparticles. The resultant nanoparticles were spherical with a mean diameter of 29 ± 3 nm. The HPPH remained intact after entrapment and the HPPH leaching out of nanoparticles was negligible for all three formulations. The highest singlet oxygen production was achieved by the post-loaded formulation, which caused the highest phototoxicity in in vitro assays. No dark toxicity was observed. Post-loaded HPPH AFPAA nanoparticles were localized to tumors in a mouse colon carcinoma model, enabling fluorescence imaging, and producing a similar photodynamic tumor response to that of free HPPH in equivalent dose.Post-loading is the promising method for loading nanoparticles with hydrophobic photosensitizers to achieve effective in vitro and in vivo PDT.

Purpurinimide methyl esters, bearing variable lengths of N-substitutions, were conjugated individually to a cyanine dye with a carboxylic acid functionality. The results obtained from in vitro and in vivo studies showed a significant impact of the linkers joining the phototherapeutic and fluorescence imaging moieties. The photosensitizer-fluorophore conjugate with a PEG linker showed the highest uptake in the liver, whereas the conjugate linked with two carbon units showed excellent tumor-imaging and PDT efficacy at 24 h postinjection. Whole body imaging and biodistribution studies at variable time points portrayed enhanced fluorescent uptake of the conjugates in the tumor compared to that in the skin. Interestingly, the conjugate with the shortest linker and the one joining with two carbon units showed faster clearance from normal organs, e.g., the liver, kidney, spleen, and lung, compared to that in tumors. Both imaging and PDT efficacy of the conjugates were performed in BALB/c mice bearing Colon26 tumors. Compared to the others, the short linker conjugate showed poor tumor fluorescent properties and as a corollary does not exhibit the dual functionality of the photosensitizer-fluorophore conjugate. For this reason, it was not evaluated for in vivo PDT efficacy. However, in Colon26 tumor cells (in vitro), the short linker was highly effective. Among the conjugates with variable linkers, the rate of energy transfer from the purpurinimide moiety to the cyanine moiety increased with deceasing linker length, as examined by femtosecond laser flash photolysis measurements. No electron transfer from the purpurinimide moiety to the singlet excited state of the cyanine moiety or from the singlet excited state of the cyanine moiety to the purpurinimide moiety occurred as indicated by a comparison of transient absorption spectra with spectra of the one-electron oxidized and one-electron reduced species of the conjugate obtained by spectroelectrochemical measurements.

Among the photosensitizers investigated, both ring-D and ring-B reduced chlorins containing the m-iodobenzyloxyethyl group at position-3 and a carboxylic acid functionality at position-17(2) showed the highest uptake by tumor cells and light-dependent photoreaction that correlated with maximal tumor-imaging [positron emission tomography (PET) and fluorescence] and long-term photodynamic therapy (PDT) efficacy in BALB/c mice bearing Colon26 tumors. However, among the ring-D reduced compounds, the isomer containing the 1'-m-iobenzyloxyethyl group at position-3 was more effective than the corresponding 8-(1'-m-iodobenzyloxyethyl) derivative. All photosensitizers showed maximum uptake by tumor tissue 24 h after injection, and the tumors exposed with light at low fluence and fluence rates (128 J/cm(2), 14 mW/cm(2)) produced significantly enhanced tumor eradication than those exposed at higher fluence and fluence rate (135 J/cm(2), 75 mW/cm(2)). Interestingly, dose-dependent cellular uptake of the compounds and light-dependent STAT3 dimerization have emerged as sensitive rapid indicators for PDT efficacy in vitro and in vivo and could be used as in vitro/in vivo biomarkers for evaluating and optimizing the in vivo treatment parameters of the existing and new PDT candidates.

The α(v)β(3) integrin receptor plays an important role in human metastasis and tumor-induced angiogenesis. Cyclic Arg-Gly-Asp (cRGD) peptide represents a selective α(v)β(3) integrin ligand that has been extensively used for research, therapy, and diagnosis of neoangiogenesis. For developing photosensitizers with enhanced PDT efficacy, we here report the synthesis of a series of bifunctional agents in which the 3-(1'-hexyloxyethyl)-3-devinylpyropheophorbide a (HPPH), a chlorophyll-based photosensitizer, was conjugated to cRGD and the related analogues. The cell uptake and in vitro PDT efficacy of the conjugates were studied in α(v)β(3) integrin overexpressing U87 and 4T1 cell lines whereas the in vivo PDT efficacy and fluorescence-imaging potential of the conjugates were compared with the corresponding nonconjugated photosensitizer HPPH in 4T1 tumors. Compared to HPPH, the HPPH-cRGD conjugate in which the arginine and aspartic acid moieties were available for binding to two subunits of α(v)β(3) integrin showed faster clearance, enhanced tumor imaging and enhanced PDT efficacy at 2-4 h postinjection. Molecular modeling studies also confirmed that the presence of the HPPH moiety in HPPH-cRGD conjugate does not interfere with specific recognition of cRGD by α(v)β(3) integrin. Compared to U87 and 4T1 cells the HPPH-cRGD showed significantly low photosensitizing efficacy in A431 (α(v)β(3) negative) tumor cells, suggesting possible target specificity of the conjugate.

Photosensitizers (PS) synthesized with the aim of optimizing photodynamic therapy (PDT) of tumors do not always fulfill their potential when tested in vitro and in vivo in different tumor models. The ATP-dependent transporter ABCG2 a multi-drug resistant pump expressed at variable levels in cancerous cells, can bind and efflux a wide range of structurally different classes of compounds including several PS used pre-clinically and clinically such as porphyrins and chlorins. ABCG2 may lower intracellular levels of substrate PS below the threshold for cell death in tumors treated by PDT, leaving resistant cells to re-populate the tumor. To determine some of the structural factors that affect substrate affinity of PS for ABCG2, we used an ABCG2 expressing cell line (HEK 293 482R) and its non-expressing counterpart, and tyrosine kinase ABCG2 inhibitors in a simple flow cytometric assay to identify PS effluxed by the ABCG2 pump. We tested a series of conjugates of substrate PS with different groups attached at different positions on the tetrapyrrole macrocycle to examine whether a change in affinity for the pump occurred and whether such changes depended on the position or the structure/type of the attached group. PS without substitutions including pyropheophorbides and purpurinimides were generally substrates for ABCG2, but carbohydrate groups conjugated at positions 8, 12, 13 and 17 but not at position 3 abrogated ABCG2 affinity regardless of structure or linking moiety. At position 3, affinity was retained with the addition of iodobenzene, alkyl chains and monosaccharides, but not with disaccharides. This suggests that structural characteristics at position 3 may offer important contributions to requirements for binding to ABCG2. We examined several tumor cell lines for ABCG2 activity, and found that although some cell lines had negligible ABCG2 activity in bulk, they contained a small ABCG2-expressing side population (SP) thought to contain cells which are responsible for initiating tumor regrowth. We examined the relevance of the SP to PDT resistance with ABCG2 substrates in vitro and in vivo in the murine mammary tumor 4T1. We show for the first time in vivo that the substrate PS HPPH (2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a) but not the non-substrate PS HPPH-Gal (a galactose conjugate of HPPH) selectively preserved the SP which was primarily responsible for regrowth in vitro. The SP could be targeted by addition of imatinib mesylate, a tyrosine kinase inhibitor which inhibits the ATPase activity of ABCG2, and prevents efflux of substrates. A PDT resistant SP may be responsible for recurrences observed both pre-clinically and clinically. To prevent ABCG2 mediated resistance, choosing non-substrate PS or administering an ABCG2 inhibitor alongside a substrate PS might be advantageous when treating ABCG2 expressing tumors with PDT.

We evaluated the accuracy of ultrasonographic diagnosis of autosomal dominant polycystic kidney disease (ADPKD) and factors influencing its prognosis in members of 17 Newfoundland families originally described in 1984. In 10 families showing genetic linkage between ADPKD and markers for the PKD1 locus, rates of false negative ultrasonographic diagnosis are estimated as 36% below the age of 10 years and 8% or less thereafter, comparable with findings of genetic linkage studies of a subset of family members. At ages above 30 years, false negative ultrasonographic diagnosis of PKD1 disease is unlikely. In 2 families in which ADPKD is not co-inherited with PKD1 markers, only 11% of members aged less than 30 years had kidney cysts. The mean (SE) age of onset of ESRD is 56.3 (1.8) years for persons with the PKD1 form of ADPKD, and 68.7 (1.7) years for affected members of families in which ADPKD is not co-inherited with PKD1 markers (P = 0.01). In the PKD1 families, age of onset of end stage renal disease (ESRD) was unrelated to the sex of the affected individual but was earlier in persons inheriting the disease from their mothers than from their fathers (50.5 vs. 64.8 years, P = 0.004), consistent with an influence of genetic imprinting on disease progression. In females with a PKD1 mutation, onset of ESRD was not influenced by parity. In PKD1 families, resemblance in age of onset of ESRD was apparent; variation was less within than between families (F = 13.0, P less than 0.0001), and risk of false negative ultrasonographic diagnosis appears largely restricted to families in which ESRD occurs relatively late.

Protoporphyrin IX (PpIX) synthesized endogenously from 5-aminolevulinic acid (ALA), is effluxed from cells expressing the ATP-dependent transporter ABCG2. Side population (SP) cells (named for their low red/blue fluorescence distribution in flow cytometry plots with ABCG2 substrates such as Hoechst) are postulated to contain cancer stem cells (CSC). The SP in U87 (human gliblastoma cell line) were more resistant to ALA-PDT than NON-SP cells. Inhibiting ABCG2 activity with the tyrosine kinase inhibitor imatinib mesylate (IM, Gleevec) during incubation with ALA increased PpIX in the SP by preventing its efflux and decreased the SP after subsequent PDT, enhancing phototoxicity. Evasion of SP cells from ALA-PDT could cause tumor recurrence from CSC. Manipulation of ABCG2 levels on the SP with small molecule modulators may be a potential strategy for enhancing PDT by decreasing the amount of substrate photosensitizer extruded from cells and lowering the threshold for phototoxicity.

Photodynamic Therapy (PDT) is emerging as a successful tool to treat both malignant and benign tumors. It involves the interaction of a photosensitizer which upon activation by the appropriate light dose, leads to a cytotoxic and vasculotoxic photodynamic reaction. Improvements in PDT in areas such as the delivery and selectivity of photosensitizers, light-delivery and overall efficacy have helped to increase its attractiveness as an option for therapy. For optimizing the PDT treatment by a "see and treat approach," we have developed a number of tumor avid photosensitizers (PS) namely HPPH-Cyanine dye conjugates or other compounds (Iodinated photosensitizers) which have the ability for Optical and/or PET imaging as well as being effective photosensitizers for treatment. Hyperthermia refers to various techniques of heat application which may be delivered as a single modality or as part of an adjunct treatment option to the existing cancer therapies. Depending upon the temperature range used, hyperthermia might either directly induce cell kill or enhance the efficacy of other treatment modalities. Hyperthermia increases blood flow within the body, which may allow for higher dose delivery of photosensitizers with subsequent increased therapeutic efficacy of PDT. Hyperthermia could also increase the sensitivity of molecular imaging. The use of multifunctional photosensitizers for imaging and PDT is an emerging area and we have developed a few such agents in our lab. We wish to explore the use of hyperthermia to improve the use of such multifunctional photosensitizers from the point of view of imaging and/or therapy. Hyperthermia can be performed either as a whole-body mode or as localized mode. Our goal is to see which of the two heating modalities offers us better outcome.

Our primary objective was to test the hypothesis that a defect in acidification is more common in patients who have idiopathic calcium phosphate kidney stones than in those whose stones are formed mainly of calcium oxalate. Additionally, other risk factors might differ for these 2 stone types. Urine pH was measured serially over 24 hours, and along with ammonium and titratable acid, it was measured before and serially after ingestion of ammonium chloride in 3 groups of subjects: 24 patients with predominantly calcium phosphate stones, 30 patients with calcium oxalate stones, and 15 health non-stone-formers. Twenty-six parameters potentially related to stone formation and acidification were assayed on urines collected over 24 hours, and 15 parameters on blood. The data base was a computerized list of 5900 analyses of stones from patients living in Newfoundland. Patients not known by their physician to have had urinary tract infection, anatomical abnormality, hyperparathyroidism, or renal tubular acidosis were asked to participate in the study. Differences between means were considered significant if p values were less than 0.05 for F by analysis of variance and also less than 0.01 by t-test. In all patients with calcium oxalate stones and all non-stone-formers, urine acidified to pH less than 5.25, but in 8 of the 23 phosphate stone formers who completed the ammonium chloride study urine failed to acidify to pH less than 5.25. As all 8 had normal values for venous pH, total CO2, and chloride, they were considered to have incomplete renal tubular acidosis (IRTA). The 8 phosphate stone formers with IRTA had greater mean values for urine pH on all 9 specimens collected serially over 24 hours (all means greater than 6.2), and after administration of ammonium chloride (p less than 0.01), as well as lower mean values for urine titratable acid excretion (p less than 0.01), both after administration of ammonium chloride and in 24-hour urine samples, compared with the remaining phosphate stone formers whose urine acidified and the oxalate and non-stone-forming control groups. Nearly all the phosphate stone formers had 1 or more risk factors for stone formation, but with frequencies not significantly higher than those found in the oxalate group. Hypercalciuria and hypocitruria were the commonest, but increased oxalate or urate also occurred. Thus, idiopathic calcium phosphate stone formation can be associated with 1 or more of several risk factors, and, with the possible exception of those with IRTA, treatment should be similar to that given to patients with calcium oxalate stones.