Etiology of microglial nodules in brains of patients with acquired immunodeficiency syndrome

Microglial nodules associated with opportunistic and HIV-related lesions are frequently found in the brains of AIDS patients. However, in many cases, the causative agent is only presumptively suspected. We reviewed 199 brains of AIDS patients with micronodular lesions to clarify their etiology by immunohistochemistry (to Toxoplasma gondii, cytomegalovirus, herpes simplex virus I/II, varicella zoster virus and HIV-p24 core protein), PCR (for herpetic viruses and Mycobacterium tuberculosis) and electron microscopy. Productive HIV infection was observed in 110 cases (55.1%): 30 cases with Toxoplasma gondii encephalitis, 30 with cytomegalovirus encephalitis, eight with multiple cerebral diseases, while in the remaining 42 cases HIV was the only pathogenetic agent. Multinucleated giant cells (hallmark of HIV infection) were found in the MGNs of 85/110 cases with HIV-related lesions; the remaining 25 cases had only p24 positive cells but no multinucleated giant cells. In these latter cases the micronodular lesions had been initially attributed to the main opportunistic agent found in the brain, or defined as subacute encephalitis. Individual microglial nodules positive for an opportunistic pathogen were generally negative for HIV antigens. In 13 cases no opportunistic agent or HIV productive infection was found. In these cases, PCR and electron microscopy examination for HIV and other viral infections were negative. Our data suggest that HIV-immunohistochemistry should be used for the etiological diagnosis of micronodular lesions in AIDS brains, even in the presence of other pathogens. After extensive search, the etiology of the microglial nodules remains unknown in only a small percentage of cases.

BK virus renal infection in a patient with the acquired immunodeficiency syndrome

BACKGROUND

We describe herein a patient with the acquired immunodeficiency syndrome and renal failure due to biopsy-proven BK virus (BKV) infection. Three months after the diagnosis of the renal viral infection, his condition remained unchanged. Although BKV has previously been shown to be associated with ureteral stenosis and renal damage in renal transplant patients, to our knowledge, the literature contains only 3 cases describing the presence of BKV lesions in the kidneys of immunosuppressed patients who had not undergone transplantation.

METHODS

The presence of BKV infection was demonstrated by means of histology, immunohistochemistry with polyclonal anti-SV40 antibody, immunoelectron microscopy, polymerase chain reaction, and enzymatic cleavage with BamHI.

RESULTS

Histologic examination revealed interstitial inflammatory infiltrates and tubules with enlarged and eosinophilic nuclei.

CONCLUSIONS

The high frequency of latent BKV infection and its reactivation during immunosuppression suggest that the possibility of its involvement in renal damage should be considered in immunocompromised patients.

Hepatic metastases from medullary thyroid carcinoma appearing twelve years after the eradication of primitive tumor: cytological and radiological aspects

We report on radiological and cytological findings from a case of medullary thyroid carcinoma (MTC) metastatizing to the liver 12 yr after the eradication of the primary neoplasm. This behavior has never before been described in a sporadic form of MTC.

Use of magnetic beads for tissue DNA extraction and IS6110 Mycobacterium tuberculosis PCR

Polymerase chain reaction (PCR) techniques are used increasingly for the diagnosis of Mycobacterium tuberculosis infection and can be used on the DNA obtained from both frozen and formalin fixed, paraffin wax embedded tissues. However, the extraction of DNA by means of the conventional phenol/chloroform method is time consuming and requires the use of potentially dangerous chemical reagents. This paper describes a method based upon the use of magnetic beads for the extraction of M tuberculosis DNA from both routinely formalin fixed, paraffin wax embedded tissues and frozen tissues. Magnetic bead extracted DNA from brain, lymph node, and lung tissues collected from patients with human immunodeficiency virus and tuberculosis was compared with that extracted using the phenol/chloroform method. The magnetic bead extraction procedure requires less than two hours, including the time necessary to dewax the tissue sections. In all cases, the DNA extracted with both methods was amplified successfully by PCR for the M tuberculosis IS6110 sequence. Magnetic bead DNA extraction can be used on both frozen and archival tissues: the method is reliable, simple, sensitive, and rapid; in addition, it does not use hazardous procedures or specialised laboratory equipment and can be used for routine DNA isolation from various human tissues.

Detection and typing of JC virus in autopsy brains and extraneural organs of AIDS patients and non-immunocompromised individuals

The distribution of JC virus (JCV) variants in the brain, lung, liver, kidney, spleen and lymph nodes collected at autopsy from AIDS patients with (Group A: 10 Ss) and without (Group B: 5 Ss) progressive multifocal leukoencephalopathy (PML) and from HIV-negative patients (Group C: 5 Ss), was examined by amplifying the JCV large T antigen (LT), the regulatory (R) and the VP1 regions. Among the samples from the PML patients, JCV DNA was detected in all of the demyelinating areas, in 60% of the lesion-free brain tissues, in 60% of the lung tissues and in 40% of the spleen and kidney tissues, whereas all liver and lymph node sections were negative. JCV DNA was also found in two of the five brain specimens, in two of the five kidney specimens, in one of the five lung specimens from the HIV-positive patients without PML and in the brain specimens from two of the five HIV-negative subjects. Nucleotide sequence analysis indicated that all of the R region amplified from extraneural tissues had rearrangements similar to those of the Mad-4 strain and that VP1-region amplified products were similar to the Mad-1 strain. In the brain specimens from two PML patients, we found a unique rearranged R region, along with a VP1 region of JCV type 2. In addition, an almost unique variant with multiple rearrangements in the R region and unusual base mutations in the VP1 region was detected in the brain sample from another PML patient. The data indicate that diffuse visceral involvement of JCV is particularly frequent in AIDS patients with PML. Moreover, the presence of rearrangements and mutations, involving different regions of the viral genome, observed in PML-affected brain tissues, could represent a risk factor for the development of PML in immunosuppressed individuals.

VZV fulminant necrotizing encephalitis with concomitant EBV-related lymphoma and CMV ventriculitis: report of an AIDS case

A case of AIDS with varicella zoster virus fulminant necrotizing encephalitis associated with cytomegalovirus ependymitis-subependymitis and a periventricular Epstein-Barr virus-related lymphoma is described. The patient had no herpes zoster cutaneous eruptions and died three days after the onset of symptoms. Varicella zoster virus and cytomegalovirus antigens were found by immunohistochemistry in the same area around a necrotic periventricular lesion; a periventricular lymphoma, large B cell type, was also observed. In situ hybridization with Epstein-Barr virus-encoded- RNAs probe was positive in about 40% of the neoplastic cells. The association of herpes-related lesions in the same cerebral region should be consistent in AIDS cases with acute neurological symptoms.

Comprehensive study on structure-activity relationships of rifamycins: discussion of molecular and crystal structure and spectroscopic and thermochemical properties of rifamycin O

The mechanism of action of rifamycins against bacterial DNA-dependent RNA polymerase has been explained on the basis of the spatial arrangement of four oxygens which can form hydrogen bonds with the enzyme. Structural descriptors are derived from X-ray diffraction crystal structures of 25 active and nonactive rifamycins. Principal component analysis is used to find the combination of structural parameters which better discriminate between active and nonactive rifamycins. Two possible mechanisms of molecular rearrangement are described which can convert nonactive into active conformations. The energy involved for conformational rearrangements is studied by molecular modeling techniques. Methyl C34 is found to play a key role for determining the geometry of the pharmacophore. Rifamycin O, reported to be active, is obtained by oxidation of rifamycin B and is studied by X-ray single-crystal diffractometry, by solution IR and NMR spectroscopy, and by thermal analysis. Surprisingly the oxidation process is totally stereospecific, and an explanation is given based on solution spectroscopic evidence. The conformation found in the solid state is typical of nonactive compounds, and molecular mechanics calculations show that a molecular rearrangement to the active conformation would require about 15 kcal/mol. Thermal analysis confirms that rifamycin O has a sterically constrained conformation. Therefore, it is likely that the antibiotic activity of rifamycin O is due either to chemical modification prior to reaching the enzyme or to conformational activation.

Renal Encephalitozoon (Septata) intestinalis infection in a patient with AIDS. Post-mortem identification by means of transmission electron microscopy and PCR

We describe the occurrence of renal Encephalitozoon (Septata) intestinalis infection in a 35-year-old AIDS patient who died with disseminated tuberculosis. The patient did not complain of specific symptoms involving the kidney or lower urinary tract during life, but at autopsy, light microscopic examination of the kidney revealed numerous small round or oval bodies in the tubules and tubular cell cytoplasm that were interpreted as intracellular protozoa. Transmission electron microscopy of tissue retrieved from paraffin-embedded samples identified these organisms as microsporidia belonging to the Encephalitozoonidae family, but did not allow definitive identification of the species of infecting parasite. This was made possible only by means of Southern blot hybridization after the polymerase chain reaction, which recognized the micro-organism as E. intestinalis.

Evaluation of PCR in detection of Mycobacterium tuberculosis from formalin-fixed, paraffin-embedded tissues: comparison of four amplification assays

We compared the sensitivities and specificities of four nested PCR assays for the detection of Mycobacterium tuberculosis from formalin-fixed, paraffin-embedded tissues. Thirty-seven autopsy samples from human immunodeficiency virus-positive patients were analyzed: 15 were M. tuberculosis positive, 11 served as negative controls, and 11 were Ziehl-Neelsen positive without cultural confirmation of M. tuberculosis. Three genomic sequences (mtp40, 65-kDa antigen gene, and IS6110) with different molecular masses and numbers of repetitions within the M. tuberculosis genome were targeted. On the IS6110 sequence, two fragments of different sizes (106 and 123 bp, respectively) were amplified with two separate pairs of primers. The highest sensitivity rates were obtained by amplifying the highly repetitive IS6110 insertion sequence, and the different primers tested showed a sensitivity ranging from 80 to 87%. Amplification of the large 223-bp fragment of the mtp40 sequence present in a single copy in the M. tuberculosis genome yielded a high rate of false-negative results, ranging from 66 to 80%. A poor sensitivity (from 47 to 60%) was also shown by PCR amplification of the 142-bp 65-kDa antigen gene. All the PCRs except that for the 65-kDa antigen gene showed a specificity of 100%. Moreover, different results were obtained with different dilutions of DNA, and DNA concentrations of 1 and 3 microg yielded the highest sensitivities depending upon which protocol was used. Application of the PCRs to the Ziehl-Neelsen-positive, culture-negative samples confirmed the sensitivities of the PCRs obtained with the control samples. In conclusion, PCR can successfully be used to detect M. tuberculosis from paraffin-embedded tissues and can be particularly useful in the validation of a diagnosis of tuberculosis in clinical settings in which the diagnosis is uncertain. However, the efficacy of PCR strictly depends on several amplification parameters such as DNA concentration, target DNA size, and the repetitiveness of the amplified sequence.

Nested polymerase chain reaction for Mycobacterium tuberculosis IS6110 sequence on formalin-fixed paraffin-embedded tissues with granulomatous diseases for rapid diagnosis of tuberculosis

We evaluated the sensitivity and specificity of a nested polymerase chain reaction (PCR) to the Mycobacterium tuberculosis IS6110 sequence on formalin-fixed paraffin-embedded tissue samples from patients with tubercular and other granulomatous lesions. Five groups of patients and samples were studied: (1) 28 samples from HIV-positive patients with tuberculosis, (2) 8 samples from HIV-negative patients with histologically suspected tuberculosis (confirmed by culture in 5 cases), (3) lymph nodes from 5 HIV-positive patients with Mycobacterium avium-intracellulare infection, (4) lymph nodes from 30 patients with sarcoidosis, and (5) specimens from 17 patients with other granulomatous diseases. The DNA was extracted from sections with a total thickness of 60 microm, and PCR amplified an internal fragment of 123 base pairs. All of the cases with M. tuberculosis infection were PCR-positive, although this sensitivity was partially related to the initial concentration of the DNA used for amplification. Two of the group 4 samples also were repeatedly positive, thus reducing the specificity of the method. All of the cases with granulomatous diseases other than sarcoidosis were negative. We propose a simplified and highly sensitive nested PCR for the diagnosis of M. tuberculosis infection on archived material in HIV-positive and HIV-negative patients.

Hepatic histology of patients with HIV infection and chronic hepatitis C treated with interferon

AIMS

To evaluate the histological changes seen in liver biopsies after interferon (IFN) treatment in patients with chronic hepatitis C and human immunodeficiency virus (HIV) infection.

METHODS

Twenty four intravenous drug users with chronic hepatitis C were investigated histologically before beginning a 12 month course of IFN treatment and 18 months later. Twelve were HIV positive, without opportunistic or other viral infections (group A), and 12 were HIV negative (group B).

RESULTS

According to alanine amino-transferase concentrations, four sustained responders and eight non-responders were found in group A; six sustained responders, five relapsers, and one non-responder were found in group B. HCV RNA became negative in one sustained responder of group A and in the six sustained responders of group B. When histological findings of biopsies performed before therapy and 18 months later were compared, no significant changes in the mean value of Knodell's index and subindices were found in group A, whereas in group B Knodell's index, piecemeal necrosis, and focal hepatocellular necrosis decreased significantly.

CONCLUSIONS

In chronic hepatitis C, coinfection with HIV showed a tendency towards a lower response to IFN, although this did not reach statistical significance; however, none of the HIV positive patients developed cirrhosis during the follow up and this should be considered in clinical management of such patients.

Predictors of cytomegalovirus disease, natural history and autopsy findings in a cohort of patients with AIDS

OBJECTIVE

To identify the predictors of acquiring cytomegalovirus (CMV) disease, and to describe natural history, therapeutic management and autopsy findings in affected patients.

DESIGN

Observational study of a consecutive cohort of AIDS patient diagnosed and followed in the same institution.

METHODS

All of the patients with CMV were included. Statistical analyses were performed to establish the risk of acquiring the disease at or after AIDS presentation, survival, and the occurrence and time of relapses in relation to maintenance therapy. The presence of CMV infection at autopsy was also investigated.

RESULTS

CMV disease was diagnosed in 304 (24.8%) out of 1,227 patients, its incidence increasing according to the year of AIDS diagnosis. Women, homosexual men, patients given zidovudine and Pneumocystis carinii pneumonia (PCP) prophylaxis before AIDS, and severely immunodepressed patients were at higher risk for the disease. CMV disease was an independent factor of worse survival (hazard ratio, 1.7 versus PCP; 95% confidence intervals, 1.28-2.13). Patients untreated during the acute phase had a 4.3 higher risk of dying than those treated. Relapses occurred less frequently and later in patients given continuous maintenance treatment (23 out of 113; 17 months) than in untreated patients (13 out of 16; 3 months) or those given discontinuous therapy (22 out of 40; 7 months), whereas survival was independent from treatment. CMV infection was found in 97 out of 134 patients at autopsy, but was unassociated with relapse.

CONCLUSIONS

CMV is a severe disease whose frequency is higher in severely immunodepressed patients. Continuous treatment leads to a lower relapse rate even if it does not change survival or eradicate the infection.

Coinfection of the central nervous system by cytomegalovirus and herpes simplex virus type 1 or 2 in AIDS patients: autopsy study on 82 cases by immunohistochemistry and polymerase chain reaction

We evaluated the frequency and histopathological features of concomitant infections of the central nervous system (CNS) with cytomegalovirus (CMV) and herpes simplex viruses type 1 or 2 (HSV1/2) in a large series of patients who had died from AIDS. Eighty-two autopsy cases with a histological diagnosis of CMV necrotizing encephalitis were examined retrospectively. CMV and HSV1/2 were detected by immunohistochemistry (IHC) with poly- and monoclonal antibodies and by nested polymerase chain reaction (PCR) for HSV 1 and 2 on DNA extracted from paraffin blocks. PCR for a beta-globin genomic sequence was performed in all IHC-positive cases to verify the integrity of extracted DNA. Concomitant CMV/HSV infections were demonstrated by IHC in 13 cases (16%); using monoclonal antibodies, HSV1 was found in 9 cases and HSV2 in 4 cases. In half of the cases, HSV1- or HSV2-positive cells represented more than 25% of immunopositive CMV cells. In all 13 cases, double immunochemical staining showed cells containing both CMV and HSV antigens. PCR for HSV1 and 2 was positive in only 7 of 13 cases (5 HSV1 and 2 HSV2). In the remaining 6 negative cases PCR for beta-globin was also repeatedly negative. HSV1 or 2 infection can be demonstrated by IHC in a significant proportion of AIDS cases with necrotizing CMV encephalitis. Nested PCR for HSV1 and 2 on DNA extracted from formalin-fixed and paraffin-embedded autopsy tissues was positive in only slighty above 50% of IHC-positive cases.

JCV-DNA and BKV-DNA in the CNS tissue and CSF of AIDS patients and normal subjects. Study of 41 cases and review of the literature

SUMMARY

We studied the distribution and localization of the human papova-viruses JCV and BKV in the central nervous system (CNS) and cerebrospinal fluid (CSF) of HIV-positive patients with and without progressive multifocal leukoencephalopathy (PML) as compared with HIV-seronegative patients. The presence of JCV-DNA and BKV-DNA was evaluated by nested polymerase chain reaction (PCR) and in situ hybridization (ISH) on CNS autopsy tissues of AIDS patients with (group A, n = 13) and without (group B, n = 16) PML and of HIV-negative patients (group C, n = 12). PCR for JCV-DNA and BKV-DNA was also performed on CSF samples collected 7-420 days before death in all the 29 AIDS patients. Tissue PCR for JCV-DNA was positive in all the cases in group A, in 44 percent of the patients in group B, and in 33 percent of the patients in group C. ISH was positive in all the cases with PML and in three AIDS cases without PML (12 percent), but negative in all the HIV-negative cases. BKV-DNA was detected in two cases from group A and in one case from group B. CSF was PCR-positive for JCV-DNA in 8 of 13 (62 percent) AIDS patients with PML, but in none of the HIV patients without PML, irrespective of the presence of JCV-DNA in CNS tissues. No CSF sample was positive for BKV-DNA. Our data demonstrates that JCV-DNA and, rarely, BKV-DNA can be detected in the CNS of immunocompromised patients with and without PML and also in the CNS of HIV-negative subjects. However, only HIV-positive patients with clinically evident PML and JCV-DNA in the brain have PCR-detectable JCV-DNA in their CSF.

JCV-DNA and BKV-DNA in the CNS tissue and CSF of AIDS patients and normal subjects. Study of 41 cases and review of the literature

SUMMARY

We studied the distribution and localization of the human papova-viruses JCV and BKV in the central nervous system (CNS) and cerebrospinal fluid (CSF) of HIV-positive patients with and without progressive multifocal leukoencephalopathy (PML) as compared with HIV-seronegative patients. The presence of JCV-DNA and BKV-DNA was evaluated by nested polymerase chain reaction (PCR) and in situ hybridization (ISH) on CNS autopsy tissues of AIDS patients with (group A, n = 13) and without (group B, n = 16) PML and of HIV-negative patients (group C, n = 12). PCR for JCV-DNA and BKV-DNA was also performed on CSF samples collected 7-420 days before death in all the 29 AIDS patients. Tissue PCR for JCV-DNA was positive in all the cases in group A, in 44 percent of the patients in group B, and in 33 percent of the patients in group C. ISH was positive in all the cases with PML and in three AIDS cases without PML (12 percent), but negative in all the HIV-negative cases. BKV-DNA was detected in two cases from group A and in one case from group B. CSF was PCR-positive for JCV-DNA in 8 of 13 (62 percent) AIDS patients with PML, but in none of the HIV patients without PML, irrespective of the presence of JCV-DNA in CNS tissues. No CSF sample was positive for BKV-DNA. Our data demonstrates that JCV-DNA and, rarely, BKV-DNA can be detected in the CNS of immunocompromised patients with and without PML and also in the CNS of HIV-negative subjects. However, only HIV-positive patients with clinically evident PML and JCV-DNA in the brain have PCR-detectable JCV-DNA in their CSF.

Clinical diagnosis of mycobacterial diseases versus autopsy findings in 350 patients with AIDS

Three-hundred fifty consecutively autopsied AIDS patients in Milan, Italy, were studied to determine the frequencies of clinical and postmortem diagnoses of mycobacterial diseases, to evaluate the clinical histories of those patients with mycobacterial diseases, and to investigate the reasons for nondiagnosis of mycobacterial diseases during life. Seventy-eight patients (22.3%) had mycobacterial diseases. In 64 cases (18.3%) the diagnosis was made antemortem and in 50 (14.2%) at autopsy; there were 36 cases of concordant clinical and postmortem diagnoses. Nontuberculous mycobacterioses (NTM) were diagnosed in 41 patients (20 clinical/postmortem diagnoses, 11 clinical diagnoses, and 10 postmortem diagnoses), extrapulmonary tuberculosis (TB) in 19 patients (7 clinical/postmorten, 8 clinical, 4 postmortem), and pulmonary TB in 18 patients (9 clinical/postmorten, 9 clinical). Patients with a clinical diagnosis of mycobacteriosis but with no pathological evidence of disease at autopsy were considered to have recovered on the basis of negative culture findings and prolonged antimycobacterial treatment. In Italian patients with AIDS, NTM occurs less frequently and TB more frequently than in American AIDS patients. At least some of the patients reported in this study seemed to have recovered from mycobacterial disease after prolonged treatment. The lack of diagnosis during life can be attributed to aspecific symptoms, a rapidly terminal course, and the presence of concomitant opportunistic diseases.

Polymorphism-structure relationships of rifamexil, an antibiotic rifamycin derivative

The polymorphism of rifamexil, a rifamycin derivative, has been investigated by thermomicroscopy, differential thermal analysis (differential scanning calorimetry-thermogravimetry), IR spectroscopy, and X-ray powder diffraction. Two crystalline forms, an amorphous material, and three solvates have been studied. The crystal structures of two solvates have also been determined by single-crystal X-ray techniques. Although the overall conformation of rifamexil is very similar in the two compounds, marked differences occur between the two crystal packings, due to differences both in the mutual orientation of the molecules and in the rifamexil-solvent interactions. Multivariate statistical methods have been used to identify the principal structural parameters determining the biological activity of the rifamycins.

Antibiotic GE2270 a: a novel inhibitor of bacterial protein synthesis. II. Structure elucidation

GE2270 A, produced by Planobispora rosea ATCC 53773, inhibits Gram-positive bacteria and anaerobes by acting on the bacterial protein synthesis. The structure has been determined by physico-chemical methods applied to the intact molecule and to the main hydrolysis products. Characterization by UV, IR, NMR (double quantum filter COSY), acid-base ionization, elemental analysis and FAB-MS indicated that GE2270 A is a highly modified peptide having MW 1,289 and formula C56H55N15O10S6, and a weak basic function, and that it belongs to the thiazolyl peptide group of antibiotics. Acid hydrolysis yielded a main product (MW 634), responsible for the chromophoric absorption, and a number of hydrolyzed products of lower MW. 13C NMR inverse techniques and MS studies (EI, positive ion chemical ionization, and collision induced dissociation FAB-MS-MS experiments) on GE2270 A, the chromophoric compound, and the other hydrolysis products led to the complete identification of the various amino acid residues and their sequence. Two out of the six chiral centers have been determined. The structure is thought to originate from modification of a chain of 14 amino acids in a process which creates 6 thiazole rings and one pyridine. The modification process also closes the linear polypeptide to form a cyclic part with an attached side-chain. GE2270 A plausibly has a similar biosynthetic origin to that of other thiazolyl peptide antibiotics such as nosiheptide and micrococcin.

Polymorphism and H-bonding of 2-[1(2H)-oxo-2-phthalazinyl]methylbenzoic acid

The three crystalline and one amorphous forms of the title compound, so far isolated, have been characterized by differential scanning calorimetry, thermomicroscopy, infrared spectroscopy and X-ray powder diffraction. From I was obtained by solidification of the melt at 200 degrees; form II by crystallization from water/ethanol 1/1; form III by grinding of II; the amorphous form by rapid cooling of the melt or by evaporation to dryness of a chloroform solution. From II melts of about 200 degrees and immediately crystallizes into form I, which melts at 210 degrees. Form III transforms into I at 165 degrees. The infrared spectra of form I is different from that of forms II and III, while each form has a different X-ray powder diffraction. From consideration of the infrared functional absorption bands, it can be derived that form I is a dimer with H-bonds between the carboxylic groups, forms II and III are monomers with intramolecular H-bond between the carboxylic group and the hydrazide carbonyl, displaying different crystal packings, and the amorphous form is a mixture of both monomers and dimers, the latters in greater amount.

Polymorphism of rifampicin

The antibiotic rifampicin shows polymorphism. Two crystalline forms, an amorphous form and four solvates (S I and S II from water; S III from tetrahydrofuran; S IV from carbon tetachloride) have been isolated and characterized by thermal analysis, infrared and X-ray powder spectroscopy. The functional I.R. bands have been interpreted as indicative of some structural features involved in the polymorphism: the intramolecular H-bonds between C23--OH and O=C--O--C25, C4--OH and O=C11, and C1--OH and O=C15. The relative physical stabilities of the various forms are reported.