Abnormality in translational regulation of catalase expression in disorders of peroxisomal biogenesis

Peroxisomal disorders are a newly described group of inherited neurological diseases. In disorders of peroxisomal biogenesis, e.g., Zellweger syndrome, owing to the lack of peroxisomes, catalase, a peroxisomal enzyme, is found to be present in the cytoplasm instead. We observed higher catalase activity (7.59 +/- 0.41 mU/ mg of protein) in cultured skin fibroblasts from Zellweger patients than in control fibroblasts (4.45 +/- 0.29 mU/mg of protein). Moreover, we also found that the majority of the catalase in Zellweger cells was present in the inactive form. The specific activities following reactivation in Zellweger and control cells were 12.1 and 4.9 mU/mg of protein, respectively. To understand the molecular basis of higher levels of catalase in Zellweger than control cells, we examined the rate of synthesis and turnover of catalase and levels of catalase mRNA and protein levels in Zellweger cells as compared with control cells. The initial rates of synthesis of catalase in Zellweger (1.68 +/- 0.15 mU/mg of protein) and control (1.51 +/- 0.14 mU/mg of protein) cells were similar. The rates of turnover of catalase in Zellweger (t1/2 = 47 +/- 8 h) and control (t1/2 = 49 +/- 7 h) were also similar. Consistent with the enzyme activity, the levels of catalase protein were higher in Zellweger cells as compared with control cells. On the other hand, there was no difference in the level of catalase mRNA between control and Zellweger cells. Although the rate of synthesis in Zellweger and control cells was initially similar, it was down-regulated to a lower level at approximately 72 h of culture in control fibroblasts as compared with Zellweger cells, which continued to synthesize catalase at the same rate up to 5 days in culture. The presence of similar levels of mRNA in control and Zellweger cells and continued synthesis of catalase in Zellweger cells at a higher level as compared with control cells suggest a loss of regulation at the translational level.

Topology of ATP-binding domain of adrenoleukodystrophy gene product in peroxisomes

Adrenoleukodystrophy (X-ALD) is a demyelinating disorder characterized by the accumulation of saturated very-long-chain fatty acids (> C22:0) due to the impaired activity of lignoceroyl-CoA ligase. The gene responsible for the disease was found to code for a 84-kDa peroxisomal integral membrane protein. Its amino acid sequence has high homology with the ATP-binding cassette superfamily of transporters and it is predicted to have six membrane-spanning segments and a putative ATP-binding domain. To define the function of ALDP, we studied the topology of its ATP-binding domain by using antibodies (1D6) against a hydrophobic domain (amino acid residues 279 to 482) and antibodies (Abct) against the C-terminal 15-amino-acid hydrophilic domain (amino acid residues 731 to 745) of ALDP. The observation of punctate fluorescence in permeabilized ALD fibroblasts, using Abct antibodies but not with antibodies against catalase, suggests that the C-terminal segment of ALDP is projected toward the cytoplasm from the peroxisomal membrane. Trypsinization of intact peroxisomes under isotonic conditions abolishes the Abct antibody recognition site, whereas the 1D6 antibodies identify a degradation product of 43-kDa protein that has been protected and retained by the membrane. This again suggests that the C-terminal portion of the ALDP protein is located on the outside (cytoplasmic) face of the peroxisomal membrane. Additional support for this conclusion was obtained by purification of the ALDP C-terminal domain, released from purified rat liver peroxisomes incubated with the cytosolic fraction, using blue-Sepharose affinity chromatography. A 47-kDa peptide retained by the column was recognized by Western blot analysis with Abct antibodies against the C-terminal sequence of ALDP and this polypeptide on polyvinylidene difluoride membrane was able to bind [gamma-32P]ATP in vitro in the presence of Mg2+. These results demonstrate that the C-terminal peptide containing the ATP-binding domains of ALDP is on the cytoplasmic surface of the peroxisomal membrane where this domain may function as an ATPase to support the functional role of ALDP in the peroxisomal membrane.

Hepatocellular and hepatic peroxisomal alterations in mice with a disrupted peroxisomal fatty acyl-coenzyme A oxidase gene

Peroxisomal genetic disorders, such as Zellweger syndrome, are characterized by defects in one or more enzymes involved in the peroxisomal beta-oxidation of very long chain fatty acids and are associated with defective peroxisomal biogenesis. The biologic role of peroxisomal beta-oxidation system, which consists of three enzymes: fatty acyl-CoA oxidase (ACOX), enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (HD), and thiolase, has been examined in mice by disrupting ACOX gene, which encodes the first and rate-limiting enzyme of this system. Homozygous (ACOX -/-) mice lacked the expression of ACOX protein and accumulate very long chain fatty acids in blood. However, these homozygous mice are viable, but growth-retarded and infertile. During the first 3-4 months of age, the livers of ACOX -/- mice reveal severe microvesicular fatty metamorphosis of hepatocytes. In such steatotic cells, peroxisome assembly is markedly defective; as a result, they contain few or no peroxisomes. Few hepatocytes in 1-3-month-old ACOX -/- mice contain numerous peroxisomes, and these peroxisome-rich hepatocytes show no fatty change. At this stage, the basal mRNA levels of HD, thiolase, and other peroxisome proliferator-induced target genes were elevated in ACOX -/- mouse liver, but these mice, when treated with a peroxisome proliferator, showed no increases in the number of hepatic peroxisomes and in the mRNAs levels of these target genes. Between 4 and 5 months of age, severe steatosis resulted in scattered cell death, steatohepatitis, formation of lipogranulomas, and focal hepatocellular regeneration. In 6-7-month-old animals, the newly emerging hepatocytes, which progressively replaced steatotic cells, revealed spontaneous peroxisome proliferation. These livers showed marked increases in the mRNA levels of the remaining two genes of the beta-oxidation system, suggesting that ACOX gene disruption leads to increased endogenous ligand-mediated transcription levels. These observations demonstrate links among peroxisomal beta-oxidation, development of severe microvesicular fatty liver, peroxisome assembly, cell death, and cell proliferation in liver.

Localization of bumetanide- and thiazide-sensitive Na-K-Cl cotransporters along the rat nephron

The present study was undertaken to investigate the mRNA localization of the two major kidney-specific Na-K-Cl transport proteins, the bumetanide-sensitive cotransporter (NKCC2 in rabbit and BSC1 in rat) and the thiazide-sensitive cotransporter (TSC). NKCC2 from rabbit and mouse has been shown to exist in three isoforms (designated A, B, and F) that differ only in a 96-bp region. The divergent region of each of the three NKCC2 isoforms was cloned from rat kidney by a polymerase chain reaction (PCR)-based strategy, and isoform-specific primers were chosen. RNA and cDNA were prepared from renal cortex and medulla and from microdissected nephron segments. Using reverse transcription (RT)-PCR, the B isoform was detected only in cortex and the F isoform only in medulla, whereas the A from was found in both. In dissected nephron segments, the B form was found exclusively in cortical thick ascending limb (CTAL) and macula densa-containing segment (MDCS), the F form only in medullary thick ascending limb (MTAL) and outer medullary collecting duct, and the A form in CTAL, MDCS, and MTAL. An additional isoform including both A and F exons was identified by direct sequencing of a 592-bp product from medulla. The AF product was found only in the medulla and was localized exclusively in MTAL. TSC mRNA was detected exclusively in the distal convoluted tubule. Differential nephron localization of NKCC2 isoforms suggests that Na-K-Cl cotransporters may differ in their transport characteristics to explain regulation of salt transport along the nephron.

Mitochondrial abnormalities in CLN2 and CLN3 forms of Batten disease

The storage of subunit c of mitochondrial ATP synthase, other hydrophobic peptides, and autofluorescent pigment in both late infantile (CLN2) and juvenile (CLN3) neuronal ceroid lipofuscinosis, but not in infantile (CLN1), has raised the question of abnormal mitochondrial function. We now report a partial deficiency in three types of fatty acid oxidation in intact skin fibroblasts from CLN2 and CLN3 patients, but not CLN1. We observed a statistically significant 33% reduction in palmitate (beta-oxidation; mainly mitochondrial) and lignocerate (beta-oxidation; mainly peroxisomal), and a 50% reduction in phytanic acid (alpha-oxidation; mainly peroxisomal) in the absence of exogenous carnitine. In contrast, when we measured fatty acid beta-oxidation (lignoceric acid and palmitic acid), in the same human skin fibroblasts, following lysis in the presence of carnitine, we found no difference in enzyme activity among normal, CLN1, CLN2, and CLN3. However, we did observe a 40% reduction in peroxisomal particulate (bound) catalase activity in CLN1 and CLN2 fibroblasts, which typically results from organellar lipid accumulation or a membrane abnormality. However, total catalase levels were normal, and Western blot analysis of this and three other major oxidant protective enzymes (Mn-dependent superoxide dismutase [MnSOD], CuZn-dependent superoxide dismutase [CuZnSOD], and glutathione peroxidase) were normal in CLN1, CLN2, and CLN3, as well as in liver from an animal (English Setter dog) model for CLN, which shows similar pathology and subunit c storage. Our data showing differences between CLN1 and forms CLN2 and CLN3 suggest some type of mitochondrial membrane abnormality as the source of the pathology in CLN2 and CLN3.

Evaluation of HBsAg carrier rate in acute viral hepatitis and high risk individuals using RPHA and ELISA

A total of 600 individuals including 500 cases of hepatitis and 100 individuals at high risk for developing hepatitis were screened for hepatitis B surface antigen (HBsAg) using reverse passive haemagglutination (RPHA) and enzyme linked immunosorbent assay (ELISA). HBsAg carrier rate in clinically diagnosed cases of hepatitis was 38% and 32.4% by RPHA and ELISA respectively. In high risk individuals, the carrier rate was 14% by RPHA and 11% by ELISA. Taking ELISA as gold standard, RPHA showed 5.33% false positivity and 0.33% false negativity. The over all correlation between RPHA and ELISA was to the tune of 82.66%.

cDNA cloning of a chick homologue of human ATPase complex subunit 4, quantitative tissue distribution and tertiary structure comparison of the ATPase domain to RecA

The ocular lens consists of a single layer of epithelial cells on its anterior surface and underlying fiber cells, which are derived from the epithelial cells by differentiation and make up the bulk of the lens. Because lens cells are segregated by age and stage of differentiation, we are using this tissue to study the role of the proteasome in differentiation. The purpose of this study is to corroborate the ATPase function of chick subunit 4 (cS4) and assess the levels of the mRNA in the differentiating lens relative to other tissues. We have generated a computer model of the tertiary structure of the ATPase domain of the cS4 of the ATPase complex that regulates the 20S proteasome. The predicted polypeptide from the cloned cDNA of cS4 (440 residues) had a calculated molecular mass of 49,182 and is 98 and 73% identical to human and yeast S4 protein sequences, respectively. A computer search for comparison with known proteins in GenBank showed that the cS4 protein sequence has a conserved region of about 200 amino acid residues including an ATP/GTP binding site and a mitochondrial energy transfer proteins signature sequence. Based on secondary structure, the computer-generated model of the ATPase domain is comparable to that of RecA, with a root mean square deviation of 0.851 from the RecA triad. mRNA in the 14-day-old chick embryo lens is derived primarily (90%) from differentiating cells. The level of cS4 mRNA determined by quantitative RT/PCR in this differentiating tissue was comparable to the cS4 mRNA levels in chick liver, heart, and brain.

The role of omental transfer in Buerger's disease: New Delhi's experience

BACKGROUND

Buerger's disease is a specific, idiopathic, recurrent, segmental, inflammatory, obliterative vascular disease involving medium-sized arteries and veins of the limbs. We performed omental transfer on a group of patients with Buerger's disease that had previously undergone lumbar sympathectomy and the results are described.

METHODS

Between January 1988 and December 1993, 100 cases of peripheral vascular disease (PVD) diagnosed as Buerger's Disease were subjected to femoral angiography. Fifty cases of angiographic intermediate/distal type blocks underwent omental transposition.

RESULTS

Of 50 patients subjected to omental transfer all had intermittent claudication, 40 had rest pain of whom 36 had non-healing ulcers, 8 had gangrene and 32 had bilateral lower limb involvement. Fifteen patients underwent bilateral omental transfer and posterior tibial artery biopsy was performed in 40. All patients showed improved skin temperature, rest pain decreased in 36 and claudication distance increased in 48. Ulcers healed in 32 of 36 patients and the line of demarcation receded in six of eight patients with gangrene.

CONCLUSIONS

Omental transfer improved skin and muscle microcirculation and forestalled the need for amputation by providing symptomatic relief and clinically arresting the progress of Buerger's disease. Omental transfer should be considered seriously as an alternative to other modalities of therapy to delay the ischaemic complications of Buerger's disease.

The successful treatment of a gender dysphoric patient with pimozide

OBJECTIVE

The case is reported of a gender dysphoric patient who responded successfully to pharmacotherapy with pimozide.

CLINICAL PICTURE

An adult male patient with a borderline learning disability presented with cross-dressing and a strong wish to undergo a sex change.

TREATMENT

Supportive psychotherapy and pharmacotherapy with pimozide was tried.

OUTCOME

There was an excellent response to pimozide 2 mg daily, with a cessation of both cross-dressing and the wish for sex reassignment. When, after 1 year, the dose was reduced to 1 mg daily, there was a rapid return of the cross-dressing and the wish for sex reassignment. An increase in the dose again led to a remission which has been maintained since then.

CONCLUSION

Pharmacotherapy with pimozide should be considered in cases of doubtful gender dysphoria.

Coordinate regulation of renal expression of nitric oxide synthase, renin, and angiotensinogen mRNA by dietary salt

Experiments were performed to examine the effect of changes in dietary salt intake on the neuronal form of the constitutive nitric oxide synthase (ncNOS, type I NOS), renin, and angiotensinogen mRNA expression in the kidney. Three groups of Sprague-Dawley rats were studied as follows: rats maintained on a 3% Na diet plus 0.45% NaCl in the drinking fluid for 7 days (high salt), rats given a single injection of furosemide (2 mg/kg i.p.) and a 0.03% Na diet for 7 days (low salt), and rats on a diet containing 0.2% Na (control). mRNA expression was assessed with reverse transcription-polymerase chain reaction (RT-PCR) methods using cDNA prepared from samples of renal cortex and microdissected tubular segments. ncNOS PCR products were quantified by comparison with a dilution series of a mutant deletion template. Compared with their respective control, ncNOS mRNA levels in renal cortical tissue were elevated in rats on a low-salt diet and reduced in rats on a high-salt diet. Similar changes were seen in the expression of renin and angiotensinogen mRNA. Dietary salt intake did not alter the mRNA levels for ncNOS from the inner medulla or for endothelial constitutive NOS (ecNOS, type III NOS) and inducible NOS (iNOS, type II NOS) in the renal cortex. ncNOS mRNA was found in glomeruli dissected with the macula densa-containing segment (MDCS), but only at marginal levels in glomeruli without MDCS. Furthermore, a low-salt diet stimulated ncNOS mRNA in glomeruli with MDCS by 6.2-fold compared with a high-salt diet. There was no effect of salt diet on ncNOS mRNA in glomeruli without MDCS or in inner medullary collecting ducts. These results suggest that ncNOS expression in macula densa cells is inversely regulated by salt intake, thus following the known response of the renin-angiotensin system to changes in salt balance.

Phytanic acid oxidation: normal activation and transport yet defective alpha-hydroxylation of phytanic acid in peroxisomes from Refsum disease and rhizomelic chondrodysplasia punctata

In humans the oxidation of phytanic acid is a peroxisomal function. To understand the possible mechanisms for the pathognomic accumulation of phytanic acid in plasma and body fluids of Refsum disease (RD) and rhizomelic chondrodysplasia punctata (RCDP), we investigated activities of various steps (activation, transport, and oxidation) in the metabolism of phytanic acid in peroxisomes isolated from cultured skin fibroblasts from control, RD, and RCDP subjects. Activation of phytanic acid was normal in peroxisomes from both RD and RCDP. Transport of phytanic acid or phytanoyl-CoA in the absence or presence of fatty acid activating cofactors (ATP, MgCl2, and CoASH) into peroxisomes isolated from RD and RCDP skin fibroblasts was also similar to that of peroxisomes from control fibroblasts. Defective oxidation of [(2,3)-3H]- or [1-14C]phytanic acid, or [1-14C]phytanoyl-CoA (substrate for the first step of alpha-oxidation) but normal oxidation of [1-14C] alpha-hydroxyphytanic acid (substrate for the second step of the alpha-oxidation pathway) in peroxisomes from RD clearly demonstrates that excessive accumulation of phytanic acid in plasma and body fluids of RD is due to the deficiency of phytanic acid alpha-hydroxylase in peroxisomes. However, in RCDP peroxisomes, in addition to deficient oxidation of [1-14C]phytanic acid or phytanoyl-CoA or [(2,3)-3H]phytanic acid, the oxidation of [1-14C] alpha-hydroxyphytanic acid was also deficient, indicating that in RCDP the activities both of alpha-hydroxylation of phytanic acid and decarboxylation of alpha-hydroxyphytanic acid are deficient. These observations indicate that peroxisomal membrane functions (phytanic acid activation and transport) in phytanic acid metabolism are normal in both RD and RCDP. The defect in RD is in the alpha-hydroxylation of phytanic acid; whereas in RCDP both alpha-hydroxylation of phytanic acid as well as decarboxylation of alpha-hydroxyphytanic acid are deficient.

Late-onset generalized disorder of peroxisomes

We diagnosed a unique peroxisomal disorder in a 32-year-old man with profound mental retardation, mild facial dysmorphism, retinal pigmentary degeneration, seizures, and sensorineural deafness. Although plasma very-long-chain fatty acid profile suggested X-linked adrenoleukodystrophy, marked reduction in fibroblast lignoceric acid oxidation and the presence of cytosolic catalase were consistent with Zellweger syndrome (ZS). Unlike ZS, functional peroxisomes were present as indicated by the density of peroxisomes (1.175 gm/ml) similar to peroxisomes from control cells and by partial deficiencies of fibroblast phytanic acid oxidation and dihydroxyacetone phosphate acyltransferase activity. These findings indicate that this patient has a previously undescribed group 3 peroxisomal disorder (multiple peroxisomal enzyme deficiencies with preserved peroxisomes).

SA gene expression in the proximal tubule of normotensive and hypertensive rats

Previous studies have shown that the SA gene is expressed at higher levels in the kidney of genetically hypertensive rats than in control strains and that in hybrid crosses of genetically hypertensive rats and normotensive controls, markers in or close to the SA gene cosegregate with blood pressure. The present studies examine the localization of the SA gene product in the kidney by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). cDNA was prepared from microdissected nephron segments from Sprague-Dawley (SD) rats, spontaneously hypertensive rats (SHRs), and Wistar-Kyoto (WKY) rats, and RT-PCR was performed using specific primers. In all three strains, SA gene mRNA was found to be abundantly expressed in proximal tubules. SA PCR product was occasionally detected at approximately 100-fold lower abundance in glomeruli, while no signal was obtained from the collecting duct, thick ascending limb of the loop of Henle, or arcuate artery. Within the proximal tubule of normotensive rats, distribution of SA mRNA was found to be strain dependent: in SD rats it was expressed at high levels in the proximal convoluted tubule, whereas in WKY rats it was restricted to the proximal straight tubule. In SHRs, SA PCR product was detected along the entire proximal tubule. Induction of hypertension by renal artery clamping (two-kidney, one-clamp Goldblatt model) did not alter the pattern of expression observed in the SD rat. These results indicate that an extension of SA gene expression to the full length of the proximal tubule accompanies spontaneous hypertension and that in nonhypertensive animals the pattern of gene product expression is more restricted but shows substantial strain variability.

Changes in the use of EEG following clinical audit

An audit of the clinical use of EEG in mentally handicapped patients was performed over a three-year period. EEG requests seemed inappropriate in more than one-quarter of cases. Changes in clinical practice during the 10 months following presentation of these audit results were examined. There was a marked reduction in EEG requests, which were subsequently used in a more cost-effective and clinically appropriate way. There was also a reduction in the time taken to process requests.

Tissue differences in antioxidant enzyme gene expression in response to endotoxin

The effect of endotoxin on antioxidant gene expression and antioxidant enzyme activity in homogenates of the heart, liver, and kidney from Sprague-Dawley rats was compared by quantitation of m-RNA and enzyme activities. Alterations in the message level for Cu-Zn superoxide dismutase (SOD), Mn SOD, and catalase varied with the tissue type, length of exposure to endotoxin, and dose of endotoxin. In general, endotoxin treatment reduced Cu-Zn SOD expression in the heart and liver, but had no noticeable effect in the kidney. Mn SOD message levels were increased in the heart and kidney but decreased in the liver. Catalase expression was reduced in the kidney and increased marginally in the heart and liver. With regard to enzyme activity, endotoxin treatment reduced Cu-Zn SOD activity in the heart, liver, and kidney. Mn SOD activity showed little change in the heart, but increased in the liver and, to a lesser extent, in the kidney. Catalase activity showed little change in the heart and kidney but was decreased at 12 h in the liver. The differing responses of tissues to the oxidant stress of endotoxin exposure should be considered when evaluating the effect of endotoxin on antioxidant enzymes.

Epoxide hydrolase in human and rat peroxisomes: implication for disorders of peroxisomal biogenesis

To understand the basis of excretion of excessive amounts of epoxydicarboxylic fatty acids (EDFA) in urine of patients with disorders of peroxisomal biogenesis (Pitt, J. J., and A. Poulos. 1993. Clin. Chim. Acta. 223: 23-29), the activity of epoxide hydrolase (EH) was measured in cultured skin fibroblasts from control subjects and patients with peroxisomal disorders. EH activity was approximately 40% lower in fibroblasts that lack intact peroxisomes (Zellweger syndrome), whereas the activity in other peroxisomal disorders (X-adrenoleukodystrophy and rhizomelic chondrodysplasia punctata) with intact peroxisomes was similar to control. To identify the specific enzyme/organelle that represents the decrease in EH activity in Zellweger cells, we have analyzed this activity in different subcellular organelles from control and Zellweger skin fibroblasts. EH activity was enriched in peroxisomes from control fibroblast. EH activity in isolated mitochondria, microsomes, or cytosol from Zellweger fibroblast was similar to that of control fibroblast. These observations indicate that deficient activity of EH in cells from Zellweger patients is due to lack of peroxisomal EH activity. The peroxisomal EH is differentially induced to a higher degree by ciprofibrate, a hypolipidemic agent and peroxisome proliferator, than EH activity in other organelles and cytoplasm. The high specific activity of EH in peroxisomes and differential induction of EH activity in peroxisomes as compared to other organelles, and the excretion of EDFA in patients who lack peroxisomes suggests that peroxisomal EH may be responsible for the detoxification of EDFA, and that this enzyme in peroxisomes may be a different protein than the EH found in other organelles.

A case in favour of one sided microscopic vasovasostomy--the New Delhi experience

Between January 1987 and December 1991 we performed vasovasal anastomosis in 60 patients who had undergone vasectomy for family planning. Of these, 30 patients were randomized for microscopic vasovasostomy and the remaining 30 patients had a macroscopic vasovasal anastomosis. Without exception the procedures were performed on one side only. Out of the 50 patients who reported for follow-up, 44 had return of spermatozoa upon semen analysis. Pregnancy resulted in 30 out of 40 patients who attempted conception (average 75%). There was one complication but no case of surgical trauma- or anaesthesia-related mishap was encountered. The results of the micro and the macro groups are analysed separately in order to draw conclusions.

Ketoconazole and other imidazole derivatives are potent inhibitors of peroxisomal phytanic acid alpha-oxidation

The imidazole antimycotics like ketoconazole, clotrimazole, bifonazole, miconazole and CO, known as powerful inhibitors of cytochrome P-450, are potent inhibitors of peroxisomal phytanic acid alpha-oxidation to pristanic acid suggesting the possible involvement of the cytochrome P-450 mono-oxygenase system in this oxidation. In contrast to the inhibition of the oxidation of [1-14C]phytanic acid, [1-14C]phytanoyl-CoA and [(2,3)-3H]phytanic acid, these drugs and CO have no effect on the oxidation of [1-14C]alpha-hydroxy phytanic acid indicating that these drugs and CO inhibit only the alpha-hydroxylation of phytanic acid. These studies using purified peroxisomes from liver and cultured human skin fibroblasts and Hep G2 cells clearly demonstrate that alpha-hydroxylation, an intermediate step in the alpha-oxidation of phytanic acid found to be impaired in Refsum Disease, is mediated by cytochrome P-450 containing enzyme.

Nitric oxide regulates peroxisomal enzyme activities

We have previously shown that peroxisomes are involved in the production and detoxification of reactive oxygen species and that peroxisomal functions are damaged by such oxygen species. Since nitric oxide is not only a cellular messenger, but also a free radical, it would be interesting to detect a connection between nitric oxide levels and peroxisomal enzyme activities. To determine if nitric oxide has an effect on the activities of peroxisomal functions and whether this effect is based solely on its chemical properties as reactive oxygen species or its action as a second messenger, effectors of the cellular nitric oxide level were applied to a cell model (human skin fibroblasts in culture) or directly to the enzymatic assays or both. If applied to the monolayer at non-cytotoxic concentrations, N-nitro-L-arginine methyl ester hydrochloride, an inhibitor of nitric oxide synthase (EC 1.14.13.39), increased catalase (EC 1.11.1.6) activity by more than 10% and decreased the activity of the peroxisomal fatty acid oxidation system by more than 10%. The effect was concentration-dependent. L-Arginine had the contrary effect. Combinations of L-arginine and N-nitro-L-arginine methyl ester hydrochloride compensated one another. If applied directly to the assays, S-nitroso-N-acetylpenicillamine and sodium nitroprusside inhibited catalase activity in a concentration-dependent manner. Sodium nitro-prusside had no effect on the peroxisomal beta-oxidation system unless cells were pretreated with N-nitro-L-arginine methyl ester overnight (50% inhibition). The results show a differential effect for the application of nitric oxide-effectors on fibroblast monolayers, cell suspensions and under assay conditions. Depending on the conditions of the incubation, nitric oxide applied to the cell monolayer at low doses acts as a second messenger in cells rather than as reactive oxygen species. Under assay conditions the effect of nitric oxide is more likely that of a reactive oxygen species because it inhibits all measured enzyme activities.

Molecular cloning and sequencing of human palmitoyl-CoA ligase and its tissue specific expression

A complimentary DNA clone encoding the entire human palmitoyl-CoA ligase has been isolated from a liver cDNA library and sequenced in it's entirety. The predicted product is a 699 amino acid protein. Southern analysis utilizing the human palmitoyl-CoA ligase gene as a probe revealed varying degrees of similarity amongst various mammalian species. The palmitoyl-CoA ligase gene is highly expressed in liver, heart, skeletal muscle and kidney, and to a lesser extent in brain, lung, placenta and pancreas. The expression of palmitoyl-CoA ligase in various tissue parallels the function of this enzyme in the metabolism of fatty acids in these tissues.

Mortality in a hospitalized mentally handicapped population: a 10-year survey

The mortality experiences of a hospitalized mentally handicapped population between 1981 and 1990 (inclusive) were examined. A continued trend for increasing longevity in both males and females was found, with mean ages at death now approaching those in the general population. The commonest cause of death was non-tubercular respiratory infection, from which patients were particularly at risk during the months of December to February (inclusive). Patients diagnosed as suffering from psychoses other than schizophrenia and mood disorder had an increased mortality and should be thoroughly investigated for the presence of organic pathology. Epilepsy and Down's syndrome were associated with increased risk of earlier death, although in the case of Down's syndrome there has been a marked increase in longevity.

A major role of class I Fc gamma receptors in immunoglobulin G anti-D-mediated red blood cell destruction by fetal mononuclear phagocytes

OBJECTIVE

To examine Fc gamma receptor (Fc gamma R) classes that direct immunoglobulin (Ig) G anti-D-mediated red blood cell interaction with fetal mononuclear phagocytes.

METHODS

Mononuclear phagocytes isolated from fetal blood and spleen at 20-35 and 12-15 weeks' gestation, respectively, were tested in a modified mononuclear phagocytosis assay against IgG anti-D-coated red blood cells in the absence and presence of Fc gamma R class-specific monoclonal antibodies as inhibitors. Monocytes from cord and adult blood served as controls.

RESULTS

In the absence of any inhibitor, attachment and phagocytosis indices of fetal monocytes were similar to those of their newborn and adult counterparts but markedly less than those of mononuclear phagocytes from fetal spleen. Blockade of the high-affinity Fc gamma RI caused a profound (more than 93%) reduction in red blood cell attachment and phagocytosis indices of fetal as well as newborn and adult monocytes. It also brought about a marked decrease in the attachment and phagocytosis indices of mononuclear phagocytes from fetal spleens (64 and 81%, respectively). With fetal spleen mononuclear phagocytes, anti-Fc gamma RII lacked any significant effect on their interaction with red blood cells, whereas anti-Fc gamma RIII caused a significant (43%) inhibition of their phagocytosis.

CONCLUSION

Immunoglobulin G anti-D-mediated attachment to and phagocytosis by fetal mononuclear phagocytes of red blood cells is well developed early during the second trimester. High-affinity Fc gamma RI plays a major role in the effector function of circulating monocytes and splenic mononuclear phagocytes, whereas Fc gamma RIII, expressed strongly on the latter effectors, participates in target ingestion.