Peroxisomal abnormality in fibroblasts from involved skin of CHILD syndrome. Case study and review of peroxisomal disorders in relation to skin disease

BACKGROUND AND DESIGN

Peroxisomal deficiency has been described in a number of syndromes characterized by chondrodysplasia punctata, including the Conradi-Hünermann (C-H) syndrome. Because of overlapping clinical features of X-chromosome inheritance, ichthyosis, and limb-reduction defects in C-H and CHILD (congenital hemidysplasia with ichthyosiform erythroderma and limb defects) syndromes, we examined peroxisomal content using diaminobenzidine cytochemistry and peroxisomal functions in fibroblasts from involved vs uninvolved skin of CHILD syndrome.

RESULTS

Fibroblasts from involved skin of a patient with CHILD syndrome accumulated cytoplasmic lipid, visualized with the fluorescent probe, nile-red. Ultrastructurally, fibroblasts of involved skin of CHILD syndrome accumulated lamellated membrane and vacuolar structures. By diaminobenzidine ultracytochemistry, fewer peroxisomes were present. Moreover, the activities of two peroxisomal enzymes, catalase and dihydroxyacetone phosphate acyltransferase, were decreased (approximately 30% of normal). However, peroxisomal oxidation of very-long-chain and branched-chain fatty acids was preserved. Moreover, plasma very-long-chain fatty acids, plasma phytanic acid, and erythrocyte plasmalogen content were normal.

CONCLUSIONS

The CHILD, C-H, and rhizomelic chondrodysplasia punctata syndromes are all characterized by ichthyosis, chondrodysplasia punctata, and limb defects, as well as peroxisomal deficiency. Thus, these syndromes may be related pathogenically. Because peroxisomes are involved in prostaglandin metabolism, peroxisomal deficiency may directly contribute to the previously reported alterations in prostaglandin metabolism in fibroblasts of involved skin of fibroblasts.

The effects of acute ethanol on growth in rat liver: steady state c-myc transcripts

In order to elucidate the effects of acute ethanol on compensatory liver growth (regeneration), the steady state c-myc mRNA levels were studied following two-thirds partial hepatectomy. After surgery, control rat livers exhibited two peaks of c-myc transcripts, at 0.5-2 h and at 8-10 h. Sham surgery did not induce c-myc mRNA expression. Ethanol (3 g/kg), administered by gavage at 1 hour prehepatectomy, had no effect on the initial peak of c-myc mRNA; however, the second peak was eliminated. Control gavage of isocaloric glucose prior to partial hepatectomy had no effects on either of the subsequent c-myc mRNA peaks. Blood alcohol levels were found to be elevated throughout the prereplicative phase. These results suggest that ethanol may disrupt proto-oncogene expression near the restriction point at the G1/S boundary of the cell cycle in hepatocytes.

Inhibition of cancer cell growth by calcium channel antagonists in the athymic mouse

The calcium channel antagonists (CCAs) amlodipine, diltiazem, and verapamil inhibited HT-39 human breast cancer cell proliferation in a concentration-dependent manner. The apparent 50% inhibitory dose values were 1.5 microM for the dihydropyridine amlodipine, 5 microM for the benzothiazapine diltiazem, and 10 microM for the phenylalkylamine verapamil. Amlodipine treatment caused a rapid concentration-dependent decrease of intracellular calcium concentration in the HT-39 cell line. Addition of 1 microM amlodipine had no effect on intracellular calcium levels, 3 microM amlodipine lowered intracellular calcium levels in the HT-39 cells by 13.7%, and 10 microM amlodipine lowered intracellular calcium levels by 33.2%. Also, lowering medium calcium levels from 2.0 mM to 0.5 microM resulted in a rapid 41.3% decrease in intracellular calcium and a concomitant 60% inhibition of HT-39 cell DNA synthesis. When HT-39 cells were transplanted into athymic mice, marked hypercalcemia developed. Serum calcium levels from control mice were 8.3 +/- 0.6 mg/dl (mean +/- SE; n = 4); those from tumor-bearing mice were 11.3 +/- 0.08 mg/dl (mean +/- SE; n = 17). Blood calcium levels correlated directly with tumor size (r = 0.91, P less than 0.01). We examined the capacity of three CCAs to specifically inhibit HT-39 tumor growth in vivo. One week after inoculation of HT-39 cells, mice were acclimated to vehicle or 0.1 mg/day amlodipine, 1.0 mg/day diltiazem, or 1.0 mg/day verpamil, in their drinking water, for 7 days. Oral administration of the dihydropyridine amlodipine (0.35 mg/day) for 10 days inhibited HT-39 breast tumor growth by 83.5 +/- 20.1% (mean +/- SE). Oral administration of diltiazem (3.5 mg/day) inhibited HT-39 breast tumor growth rate by 46.5 +/- 6.6% over a 2-week measurement period, and verapamil (3.5 mg/day) inhibited tumor growth rate by 68.2 +/- 9.7% (mean +/- SE). The CCAs had no effect on mouse body weight or gross organ morphology at the concentrations used. Lack of depolarization-induced calcium fluxes in the HT-39 cell line suggests that these cells do not express voltage-operated calcium channels. Thus, our study correlates an effect of amlodipine to lower intracellular calcium levels, by a mechanism not known at present, with its effect to inhibit HT-39 cell proliferation. These findings are important since they demonstrate that amlodipine and other CCAs with known pharmacodynamics and side effects act to blunt breast tumor progression in vivo.

Dose, time, and fraction size issues for late effects in head and neck cancers

This paper contains a statistical analysis of the dose-time factors influencing late complications in 784 patients with squamous cell carcinomas of the pharynx or larynx treated with external beam irradiation only at the University of Florida. The patients include 560 who received continuous course once-a-day therapy, 116 who received twice-a-day treatment, and 108 who received a once-a-day split course regimen. Both 2+ and 3+ complications were considered. Fifty-six patients developed either of these complications. The factors included in the analysis were site and size of the primary, total dose, fraction size, and treatment time. The linear-quadratic model was used to incorporate fraction size into the analysis. Proportional hazards analysis, which models the time to occurrence of the late complication, was used to quantify the joint influence of the above patient and fractionation variables on the incidence of late effects. The occurrence of the late effects was heterogeneous, with only a weak relationship to the patient and fractionation variables. The influence of the size of the primary was significant, with larger primaries associated with higher complication rates independent of fractionation variables. For oropharynx primary sites there was no significant effect of the fractionation variables. For larynx and hypopharynx, excluding T1-T2 true vocal cord, there was a significant effect of total dose and fraction size. The alpha/beta ratio was estimated to be 7.8 Gy (95% confidence interval, 3.0, infinity). There was no significant effect of overall treatment time. The estimated 2+ complication rate at 1 year from 68 Gy given in 2 Gy fractions in 50 days is 0.1% for T 1-2 vocal cord, 4.1% for T1-T2 supraglottic larynx, 3.8% for T3 supraglottic larynx and vocal cord, 14.9% for T4 supraglottic larynx, 6.7% for T1-T2 tonsil and soft palate, 7.6% for T3-T4 tonsil and soft palate, 7.0% for T1-T2 pyriform sinus and pharyngeal wall, and 13.0% for T3-T4 pyriform sinus and pharyngeal wall.

Estimation of time since exposure for a prevalent cohort

In natural history studies of human immunodeficiency virus type 1 (HIV-1) infection a substantial proportion of participants are seropositive at time of enrollment in the study. These participants form a prevalent subcohort. Estimation of the unknown times since exposure to HIV-1 in the prevalent subcohort is of primary importance for estimation of the incubation time of AIDS. The subset of the cohort that tested negative for antibody to HIV-1 at study entry and was observed to seroconvert forms the incident subcohort that provides longitudinal data on markers of maturity (that is, duration) of infection. We use parametric life table regression models incorporating truncation to describe the conditional distribution (imputing model) of the times since seroconversion given a vector of the markers of maturity. Using the fitted model and the values of the markers of maturity of infection provided by the seroprevalent subcohort at entry into the study, we can impute the unknown times since seroconversion for the prevalent subcohort. We implement multiple imputation based on a model-robust estimate of the covariance matrix of parameters of the imputing model to provide confidence intervals for the geometric mean of the time since seroconversion in the prevalent subcohort, and to compare maturity of infection of cohorts recruited in different cities. The accuracy of imputation is further validated by comparisons of imputation-based estimates of AIDS incubation distribution in the seroprevalent subcohort with more direct estimates obtained from the seroincident subcohort.

The influence of dose and time on wound complications following post-radiation neck dissection

Data on 205 patients who were treated with a planned unilateral neck dissection following radiation therapy were analyzed with the purpose of understanding how treatment factors affect the incidence of wound complications. There were 27 occurrences of wound complication in the patient series. Logistic regression was used to analyze the data. We found that the surgical technique of flap reconstruction gave a significant increase in wound complications. There was a suggestion, although not statistically significant, that higher total doses increased the complication rate, that lower fraction sizes reduced the complication rate, and that longer overall radiotherapy treatment times were associated with higher complication rates. There was no association between the incidence of complications and the time interval between the end of radiotherapy and surgery.

The effect of zidovudine treatment on serum neopterin and beta 2-microglobulin levels in mildly symptomatic, HIV type 1 seropositive individuals

Sixty-one subjects with mildly symptomatic human immunodeficiency virus (HIV) infection were included in a double-blind, randomized, placebo-controlled trial of zidovudine (part of AIDS Clinical Trials Group protocol 016, ACTG 016) to evaluate changes in the serum immune activation markers neopterin and beta 2-microglobulin (beta 2M) as early markers of the antiviral effect of zidovudine on HIV type 1 (HIV-1) infection. The mean values of serum neopterin and beta 2M levels in 27 placebo-treated subjects tended to increase with time. The mean value of neopterin in 34 subjects receiving zidovudine decreased at 4 weeks (15.76 nmol/L before treatment to 12.73 nmol/L, p = 0.001). The maximum reduction was seen at 8 weeks of treatment (10.78 nmol/L, p less than 0.0001). Subsequently, the mean value of serum neopterin increased but remained below the pretreatment value for more than a year. Serum beta 2M levels decreased (from 3.01 to 2.69 mg/L at 4 weeks, p = 0.01) and reached the lowest level at 8 weeks (2.45 mg/L, p = 0.0002) in zidovudine recipients. The mean beta 2M level returned to pretreatment value at approximately 24 weeks of the treatment. There was a close correlation between changes from baseline in serum neopterin and beta 2M during the first 16 weeks of the zidovudine therapy, but not later. Subjects with greater reductions of serum neopterin or beta 2M tended to maintain lower levels of these markers with continued zidovudine administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Rhinocerebral mucormycosis following bone marrow transplantation

Rhizopus oryzae was the causative organism in a fatal case of rhinocerebral and then pulmonary mucormycosis in a patient cured of her underlying leukaemia by bone marrow transplantation. We discuss the risk factors involved and the need for maintaining a high index of suspicion of fungal infection in the late post-transplant period.

Effect of CD4+ cell count measurement variability on staging HIV-1 infection

A single CD4+ cell count (CD4) measurement is often used to stage HIV-1 infection, decide when to initiate prophylactic therapy and inform patients, and may soon even define AIDS onset. Documentation of the reliability and validity of employing CD4 for the above purposes in a population-based setting is needed. We utilized data from 4,954 homosexual/bisexual men followed over 6 years, with CD4 testing at 6 month intervals, to study the timing of CD4-based staging of HIV-1 disease and quantify and evaluate the potential impact of CD4 measurement error. The median time from seroconversion to first CD4 test below 500 x 10(6)/L or clinical AIDS was 1.70 years, and the first CD4 test below 200 x 10(6)/L or clinical AIDs was 5.29 years. The time from first testing less than 500 x 10(6)/L to clinical AIDS in untreated men was 5.55 years. With confirmatory retesting, these times were significantly lengthened. The 95% confidence ranges for the true CD4 state in individuals with measured CD4 of 500 and 200 x 10(6)/L are at least (297 x 10(6), 841 x 10(6)/L) and (118 x 10(6), 337 x 10(6)/L), respectively. Without confirmatory retesting, individuals with true CD4 remaining at 700 x 10(6) and 280 x 10(6)/L have at least a 40% chance for one of five CD4 measurements to fall below guideline limits of 500 x 10(6) and 200 x 10(6)/L, respectively. Confirmatory retesting can reduce these probabilities to as low as 4%.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of hyperfractionation on spinal cord response to radiation

The T10-L2 level of the spinal cord of C3Hf mice was irradiated using a conventionally fractionated regimen of 2.0 Gy once daily or a hyperfractionated regimen of 1.2 Gy twice daily separated by 8 hr. After a fractionated dose of 24-60 Gy given by either regimen, a top-up dose of 15 Gy was given. Hind limb strength was then measured weekly for 15 months. The time to onset of paralysis was inversely associated with the total dose. Overall, the spinal cord was not spared by hyperfractionation to the extent predicted by the modified Ellis power law or the linear-quadratic model. The threshold dose for the development of paralysis was higher in the hyperfractionated than in the conventionally fractionated group. However, the latent period for paralysis and the dose producing hind limb paralysis in 50% of the mice (ED50) were not significantly different between the two regimens. The continuation of the process of sublethal damage (SLD) repair in the spinal cord beyond 8 hr after irradiation may have influenced these results. The slow component of SLD repair should be considered in the design of hyperfractionated or accelerated radiation therapy schedules for clinical use.

The unseen sample in cohort studies: estimation of its size and effect. Multicenter AIDS Cohort Study

Recruitment of disease-free subjects into cohort studies and measurement of their time from exposure/infection to disease selectively excludes individuals (the unseen sample) who had earlier exposure and who have shorter times to disease. The unseen and observed samples may differ in other characteristics in addition to incubation period and exposure/infection time. For data with known truncation times, we develop non-parametric maximum likelihood estimates of the size, exposure/infection dates and distribution of incubation time in the unseen sample. We provide procedures to estimate and compensate for the biasing effects due to exclusion of the unseen sample in descriptive and survival analysis. We give consistency properties of these estimates and assess variability using bootstrap methods. One can use imputation to derive the above estimates from data with unknown truncation times that have been estimated parametrically. Application is made to an AIDS cohort study of over 5000 homosexual men. Important estimates obtained from this application are the annual seroconversion rates from 1978 to 1983, not otherwise obtainable in this study population.

Estimating the 1978-1990 and future spread of human immunodeficiency virus type 1 in subgroups of homosexual men

The authors studied the historical spread of human immunodeficiency virus type 1 (HIV-1) infection in homosexual/bisexual men and projected its future spread in these men using data from an AIDS-free cohort recruited during late 1984 in Baltimore, Maryland; Chicago, Illinois; Los Angeles, California; and Pittsburgh, Pennsylvania. Dates of preentry seroconversion in HIV-1 seroprevalent men were estimated using study entry values of hematologic variables influenced by HIV-1 infection. The authors used survival methods incorporating truncation to determine numbers/dates of seroconversion for men with a pre-1984 AIDS diagnosis who were selectively excluded by design from the 1984 AIDS-free cohort. Overall, the annual seroconversion hazard rose progressively from 0.4% in 1978 to 13.8% in 1983, dropped to 4.6% in 1985, and remained relatively stable at 1.1-2.2% from 1986 to 1990. By January 1990, almost 46% of men who were seronegative in 1978 had seroconverted. The authors estimated historical rates of spread by city, age, education, and ethnicity to examine the effects of these factors in the early and continuing stages of the HIV-1 epidemic. There were striking differences among cities with respect to pre-1985 seroconversion rates but not with respect to post-1985 seroconversion rates. Age, education, and ethnicity were all associated with 1978-1990 seroconversion rates. Future seroconversion among homosexual men was predicted assuming that the "stabilized" 1986-1990 hazards (stratified by age) observed here will be representative of future rates. Truncated Kaplan-Meier methods gave the probability of a seronegative 20-year-old man's remaining seronegative in subsequent years. Such a man has a 20.2% chance of seroconverting before reaching the age of 25 years (a 4.4% yearly hazard). The annual hazard drops to 2.5% between 25 and 30 years, to about 1.5% between 30 and 45 years, and to 1.0% between 45 and 55 years. The overall probability of seroconversion prior to age 55 years is about 50%, with seroconversion still continuing at and after age 55. Given that this cohort consists of volunteers receiving extensive anti-HIV-1 transmission education, the future seroconversion rates of the general homosexual population may be even higher than those observed here.

Time-dose factors in positive neck nodes treated with irradiation only

This article describes an analysis of time-dose and clinical factors which affect the 2 year rate of control of cervical node metastases from squamous cell carcinoma of the head and neck following external beam radiotherapy in a series of 140 patients. We find that node diameter and normalized total dose are the most important factors, and that overall treatment time is not statistically significant.

Functional characterization of human recombinant apolipoprotein AIV produced in Escherichia coli

Apolipoprotein AIV (apoAIV), a protein which is known to activate the enzyme lecithin: cholesterol acyltransferase, to bind to apoAI/AII receptor sites and also to promote cholesterol efflux from adipose cells, may play an important role in reverse cholesterol transport. In this report, the high-level production of soluble recombinant mature human apoAIV (isoform 1) in Escherichia coli is described. The recombinant protein was purified by avoiding lipid extraction or denaturation. The apoAIV preparation was analysed by its reactivity with antibodies raised against human apoAIV, SDS-gel electrophoresis, isoelectric focusing and N-terminal sequencing. The purified recombinant protein retains an extra methionine at the N-terminus. Purified recombinant and natural apoAIV proteins were indistinguishable with regard to their denaturation properties, thermo-stability or their fluorescence emission properties in the presence of various quantities of a quenching agent. Complexes of ApoAIV with L-alpha-dimyristoyl-glycerophosphocholine (Myr2GroPCho), glycerophosphocholine (GroPCho), or L-alpha-1-palmitoyl-2-oleoylglycerophosphocholine (PamOleGroPCho) prepared from plasmatic and from recombinant apoAIV proteins have similar densities as revealed by analytical centrifugation. They also share the same cofactor properties for the lecithin:cholesterol acyltransferase reaction. Recombinant apoAIV complex with Myr2GroPCho was also able to bind to the same apoAI/AII receptor sites and to promote cholesterol efflux to an equal extent from adipose cells. It is concluded that the recombinant protein is functionally identical to the plasmatic apoAIV and may therefore be very useful in helping to elucidate the physiological role of apoAIV.

Estimating the AIDS incubation period from a prevalent cohort

Data from a cohort study of 177 homosexual or bisexual men enrolled in Los Angeles in 1982 and 1983 are used to estimate the incubation period distribution of acquired immunodeficiency syndrome (AIDS). The statistical method used is parametric modeling of the joint distribution of the date of human immunodeficiency virus infection and the time from infection to the onset of AIDS. With this method, the unknown dates of infection and the fact that individuals who developed AIDS prior to the enrollment date are excluded from the sample is taken into account. The estimated proportion of individuals who develop AIDS within 4 years of infection is 0.10 (95% confidence interval 0.05-0.21) and that within 8 years of infection is 0.45 (95% confidence interval 0.30-0.60). These proportions are consistent with those obtained from other cohort studies and through other statistical approaches.

Multiple tissue-specific elements control the apolipoprotein E/C-I gene locus in transgenic mice

To investigate the mechanisms controlling tissue-specific expression of the human apolipoprotein (apo) E/C-I gene locus, human apoE and apoC-I gene constructs containing various lengths of the 5'-flanking or 3'-flanking region were used to create transgenic mice. Several essential tissue-specific regulatory elements were identified in the region between the apoE and the apoC-I genes, as well as in a distal domain found downstream of the apoC-I gene. Most notably, transcription of both the apoE and apoC-I genes in the liver, their major site of expression, required downstream regulatory elements, possibly located within a common regulatory domain more than 2 kilobases 3' of the apoC-I gene (about 14 kilobases downstream of the apoE gene promoter). In the region between the apoE and apoC-I genes, a single strong positive element directed apoE and apoC-I gene expression in the skin. The intergenic region also contained elements that stimulated apoE gene expression in the brain and silenced apoE gene expression only in the kidney. These results demonstrate that multiple independent regulatory elements control expression of the human apoE/C-I gene locus in various tissues. Transgenic mice expressing human apoC-I in the liver exhibited plasma triglyceride levels that were 2-3-fold higher than those in control mice, an effect not found when transgenic human apoE was produced. This result suggests that apoC-I may modulate the metabolism of triglyceride-rich lipoproteins.

Repopulation of mouse jejunal crypt cells

The regenerative response to radiation of mouse jejunal crypt cells was investigated using a three fraction experiment. The time between the second and third fraction was varied between 5 and 60 h, and the dose in each of the three fractions was different. The data show that the onset of regeneration is within 14 h of the first dose and possibly earlier. The doubling time of the clonogenic cells during repopulation is estimated to be between 5 and 10 h, with the most likely value approximately 6 to 7 h. The data also show that the time course of repopulation in an acutely responding tissue depended in a complex way on the fractionation scheme. The implications of this for radiotherapy are that simple formulas are unlikely to be accurate predictors of acute effects in altered fractionation schemes. Detailed mathematical modelling of the data is undertaken using a model which consists of a single dose survival curve, a part to incorporate the regenerative response and a part to accommodate the delayed onset of regeneration. The model is shown to give a good, although not perfect, fit to the data. A mathematical derivation is given of the expected number of crypts following the 3 dose radiation schedule. This derivation takes into account the fact that any crypt could be denuded of cells prior to the final dose and hence not repopulate, and thus the formula given is necessarily more complex than previous formulas which were based on simpler models.

Applications of a computer simulation model of the natural history of CD4 T-cell number in HIV-infected individuals

Data from the Multicenter AIDS Cohort Study (MACS) of 1637 gay men, recruited in 1984 and 1985 in Los Angeles and followed at 6-monthly intervals, are used to develop a computer simulation model of the typical pattern of CD4 T-cell number changes in HIV-infected AIDS-free subjects. The empirical model incorporates the following features: (1) within-person and between-person variability in CD4 measurements; (2) variation in the rates of decline of CD4 values; (3) variation in the level of CD4 at which clinical AIDS is diagnosed, and (4) greater absolute variation in CD4 values in men with high CD4 levels compared with men with low CD4 values. Three applications of the model to assist in the design and interpretation of clinical trials are given. Further applications to clinical trials and to estimate the current and future spectrum of HIV-mediated immunological disease in the USA, as measured by the CD4 values, are discussed.

How well is the probability of tumor cure after fractionated irradiation described by Poisson statistics?

The probability of tumor cure in a homogeneous population of tumors exposed to fractionated radiotherapy was modeled using numerical simulations and compared with the predictions of Poisson statistics, assuming exact knowledge of the relevant tumor parameters (clonogen number, radiosensitivity, and growth kinetics). The results show that although Poisson statistics (based on exact knowledge of all parameters) accurately describes the probability of tumor cure when no proliferation occurs during treatment, it underestimates the cure rate when proliferation does occur. In practice, however, the inaccuracy is not likely to be more than about 10%. When the tumor parameters are unknown and are estimated by fitting an empirical Poisson model to tumor-cure data from a homogeneous population of proliferative tumors, the resulting estimates of tumor growth rate and radiosensitivity accurately reflect the true values, but the estimate of initial clonogen number is biased downward. A new formula that is more accurate than Poisson statistics in predicting the probability of tumor cure when proliferation occurs during treatment is discussed.

Two quick estimates of the HIV prevalence in homosexual men in Los Angeles, New York and San Francisco. The Multicenter AIDS Cohort Study

Two rough methods are given to estimate the combined HIV prevalence in Los Angeles, New York and San Francisco in homosexual men. Both methods are related to the back calculation technique, and use AIDS surveillance data and information obtained from the Multicenter AIDS Cohort Study. Both methods suggest that the combined HIV prevalence is approximately 100,000, with a possible range of 80,000-140,000.

In the absence of a downstream element, the apolipoprotein E gene is expressed at high levels in kidneys of transgenic mice

Human apolipoprotein (apo) E gene constructs with 30 or 5 kilobases of 5'-flanking and 1.5 kilobases of 3'-flanking regions were used to create transgenic mice. High levels of human apoE mRNA were present in the transgenic kidney, but none was detected in the liver, which is normally the major source of apoE. When a construct with 5 kilobases of 5'- and 23 kilobases of 3'-flanking regions was used, only trace levels of human apoE mRNA were detected in the kidney, whereas high levels were found in the liver. These results indicated that regulatory elements downstream of the human apoE gene interacted with the transcription initiation complex to stimulate gene expression in the liver while suppressing expression in the kidney. In each case, human apoE was secreted into the plasma. The source of human apoE in the transgenic kidney was the epithelial cells lining the proximal tubule and Bowman's capsule.