Negative autoregulation of HNF-4alpha gene expression by HNF-4alpha1

HNF-4alpha (hepatocyte nuclear factor-4alpha) is required for tissue-specific expression of many of the hepatic, pancreatic, enteric and renal traits. Heterozygous HNF-4alpha mutants are inflicted by MODY-1 (maturity onset diabetes of the young type-1). HNF-4alpha expression is reported here to be negatively autoregulated by HNF-4alpha1 and to be activated by dominant-negative HNF-4alpha1. Deletion and chromatin immunoprecipitation analysis indicated that negative autoregulation by HNF-4alpha1 was mediated by its association with the TATA-less HNF-4alpha core promoter enriched in Sp1, but lacking DR-1 response elements. Also, negative autoregulation by HNF-4alpha1 was independent of its transactivation function, being similarly exerted by transcriptional-defective MODY-1 missense mutants of HNF-4alpha1, or under conditions of suppressing or enhancing HNF-4alpha activity by small heterodimer partner or by inhibiting histone deacetylase respectively. Negative autoregulation by HNF-4alpha1 was abrogated by overexpressed Sp1. Transcriptional suppression by HNF-4alpha1 independently of its transactivation function may extend the scope of its transcriptional activity to interference with docking of the pre-transcriptional initiation complex to TATA-less promoters.

Transcriptional suppression of human microsomal triglyceride transfer protein by hypolipidemic insulin sensitizers

Microsomal triglyceride transfer protein (MTP) catalyzes the assembly and secretion of liver triglyceride-rich lipoproteins. The human MTP (hMTP) promoter activity is reported here to be suppressed by HNF-4alpha ligand antagonists (e.g., Medica analogs) or by PPARgamma ligand agonists (e.g., thiazolidinediones), thus accounting for their hypolipidemic activity in humans. Suppression of liver hMTP by Medica analogs or by thiazolidinediones was mediated by the TAAA sequence that serves as non-canonical TATA box of the hMTP core promoter. MTP suppression was evident in the specific context of the wild type hMTP core promoter, but not in the context of the mutated rodent-conforming hMTP core promoter governed by a canonical TATA box conjoined with its proximal (-50/-38)DR-1 element. hMTP suppression by Medica analogs or thiazolidinediones mediated by hMTP TAAA was independent of HNF-4alpha or PPARgamma. hMTP suppression by Medica analogs, but not by thiazolidinediones, was further complemented by inhibition of HNF-4alpha transcriptional activity transduced by the distal (-83/-70)DR-1 element of hMTP promoter. hMTP promoter activity was unaffected by PPARalpha activation. Furthermore, in contrast to hMTP, the promoter activity of the rodent-conforming hMTP was robustly activated by Wy-14,643-activated PPARalpha or by thiazolidinedione-activated PPARgamma. Transcriptional activation by PPARalpha or PPARgamma of the rodent-conforming, but not the wild type hMTP gene promoter, resulted from the species-specific context of the respective proximal DR-1 elements. Hence, suppression of hMTP transcription by hypolipidemic insulin sensitizers requires the specific context of hMTP core promoter. In light of the species-specific context of MTP core promoters, the rodent MTP promoter may not substitute for the human promoter when searching for hypolipidemic MTP suppressors.

Thioesterase activity and acyl-CoA/fatty acid cross-talk of hepatocyte nuclear factor-4{alpha}

Hepatocyte nuclear factor-4alpha (HNF-4alpha) activity is modulated by natural and xenobiotic fatty acid and fatty acyl-CoA ligands as a function of their chain length, unsaturation, and substitutions. The acyl-CoA site of HNF-4alpha is reported here to consist of the E-F domain, to bind long-chain acyl-CoAs but not the respective free acids, and to catalyze the hydrolysis of bound fatty acyl-CoAs. The free acid pocket, previously reported in the x-ray structure of HNF-4alpha E-domain, entraps fatty acids but excludes acyl-CoAs. The acyl-CoA and free acid sites are distinctive and noncongruent. Free fatty acid products of HNF-4alpha thioesterase may exchange with free acids entrapped in the fatty acid pocket of HNF-4alpha. Cross-talk between the acyl-CoA and free fatty acid binding sites is abrogated by high affinity, nonhydrolyzable acyl-CoA ligands of HNF-4alpha that inhibit its thioesterase activity. Hence, HNF-4alpha transcriptional activity is controlled by its two interrelated acyl ligands and two binding sites interphased in tandem by the thioesterase activity. The acyl-CoA/free-acid and receptor/enzyme duality of HNF-4alpha extends the paradigm of nuclear receptors.

Transcriptional regulation of human microsomal triglyceride transfer protein by hepatocyte nuclear factor-4alpha

Microsomal triglyceride transfer protein (MTP) catalyzes the assembly of triglyceride (TG)-rich apolipoprotein B-containing liver (e.g., VLDL) and intestinal (e.g., chylomicron) lipoproteins. The human MTP gene promoter is reported here to associate in vivo with endogenous hepatocyte nuclear factor-4alpha (HNF-4alpha) and to be transactivated or transsuppressed by overexpressed or by dominant negative HNF-4alpha, respectively. Human MTP (hMTP) transactivation by HNF-4alpha is accounted for by the concerted activity of distal (-83/-70) and proximal (-50/-38) direct repeat 1 elements of the hMTP promoter that bind HNF-4alpha. Transactivation by HNF-4alpha is specifically antagonized by chicken ovalbumin upstream promoter. Transcriptional activation of hMTP by HNF-4alpha is mediated by HNF-4alpha domains engaged in ligand binding and ligand-driven transactivation and is further complemented by HNF-4alpha/HNF-1alpha synergism that involves the HNF-4alpha activation function 1 (AF-1) domain. hMTP transactivation by HNF-4alpha is specifically inhibited by beta,beta-tetramethyl-hexadecanedioic acid acting as an HNF-4alpha antagonist ligand. hMTP transactivation by HNF-4alpha may account for the activation or inhibition of MTP expression and the production of TG-rich lipoproteins by agonist (e.g., saturated fatty acids) or antagonist [e.g., (n-3) PUFA, hypolipidemic fibrates, or Methyl-substituted dicarboxylic acid (Medica) compounds] HNF-4alpha ligands.

A placebo-controlled pilot study of the ampakine CX516 added to clozapine in schizophrenia

CX516, a positive modulator of the glutamatergic alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor, improves performance in tasks requiring learning and memory in animals. CX516 was added to clozapine in 4-week, placebo-controlled, dose-finding (N = 6) and fixed-dose (N = 13) trials. CX516 was tolerated well and was associated with moderate to large, between-group effect sizes compared with placebo, representing improvement in measures of attention and memory. These preliminary results suggest that CX516 and other "ampakines" hold promise for the treatment of schizophrenia.

Suppression of hepatocyte nuclear factor-4alpha by acyl-CoA thioesters of hypolipidemic peroxisome proliferators

Hepatocyte nuclear factor-4alpha (HNF-4alpha) modulates the expression of liver-specific genes that control the production (e.g. apolipoprotein [apo] A-I and apo B) and clearance (e.g. apo C-III) of plasma lipoproteins. We reported that the CoA thioesters of amphipathic carboxylic hypolipidemic drugs (e.g. clofibric acid analogues currently used for treating hyperlipidemia in humans and substituted long-chain dicarboxylic acids) were formed in vivo, bound to HNF-4alpha, inhibited its transcriptional activity, and suppressed the expression of HNF-4alpha-responsive genes. Hypolipidemic PPARalpha (peroxisome proliferator-activated receptor alpha) activators that were not endogenously thioesterified into their respective acyl-CoAs were shown to be effective in rats but not in humans, implying that the hypolipidemic activity transduced by PPARalpha in rats was PPARalpha-independent in humans. The suppressed acyl-CoA synthase of PPARalpha knockout mice left unresolved the contribution made by the acyl-CoA/HNF-4alpha pathway to the hypolipidemic effect of PPARalpha agonists in rodents. Hence, suppression of HNF-4alpha activity by the CoA thioesters of hypolipidemic "peroxisome proliferators" may account for their hypolipidemic activity independently of PPARalpha activation by their respective free carboxylates. The hypolipidemic activity of peroxisome proliferators is mediated in rats and humans by the PPARalpha and HNF-4alpha pathways, respectively.

Clozapine in the treatment of refractory psychotic mania

OBJECTIVE

The efficacy of clozapine was examined in a group of patients with treatment-refractory bipolar disorder, manic type with psychotic features.

METHOD

Twenty-two subjects with treatment-refractory bipolar disorder with active manic and psychotic symptoms participated in a 12-week open-label trial of clozapine. After a 2-10-day drug washout period, patients began treatment with clozapine at 25 mg/day; the dose was increased 25 mg/day (as tolerated) to a maximum level of 550 mg/day. Patients were evaluated longitudinally over the course of the study with the Brief Psychiatric Rating Scale (BPRS), the Young Mania Rating Scale, and the Clinical Global Impressions (CGI) scale.

RESULTS

Fourteen of the 22 subjects in the study continued taking clozapine for at least 10 of the 12 weeks. Among the entire group, mean improvements of 56. 7%, 56.6%, and 39.1% were seen on the BPRS, Young Mania Rating Scale, and CGI, respectively. Seventeen of the 22 subjects (77.3%) experienced at least a 20% improvement in scores on all three scales.

CONCLUSIONS

The findings from this open-label study, which are consistent with previous retrospective studies, case reports, and one other open-label prospective study, suggest that clozapine is an effective agent for patients with treatment-refractory psychotic mania.

Fatty acyl-CoA thioesters are ligands of hepatic nuclear factor-4alpha

Dietary fatty acids specifically modulate the onset and progression of various diseases, including cancer, atherogenesis, hyperlipidaemia, insulin resistances and hypertension, as well as blood coagulability and fibrinolytic defects; their effects depend on their chain length and degree of saturation. Hepatocyte nuclear factor-4alpha (HNF-4alpha) is an orphan transcription factor of the superfamily of nuclear receptors and controls the expression of genes that govern the pathogenesis and course of some of these diseases. Here we show that long-chain fatty acids directly modulate the transcriptional activity of HNF-4alpha by binding as their acyl-CoA thioesters to the ligand-binding domain of HNF-4alpha. This binding may shift the oligomeric-dimeric equilibrium of HNF-4alpha or may modulate the affinity of HNF-4alpha for its cognate promoter element, resulting in either activation or inhibition of HNF-4alpha transcriptional activity as a function of chain length and the degree of saturation of the fatty acyl-CoA ligands. In addition to their roles as substrates to yield energy, as an energy store, or as constituents of membrane phospholipids, dietary fatty acids may affect the course of a disease by modulating the expression of HNF-4alpha-controlled genes.

Obsessions and compulsions as a distinct cluster of symptoms in schizophrenia: a neuropsychological study

Using neurocognitive testing, the present study assessed whether obsessions and compulsions could represent a distinct cluster of symptoms in schizophrenia. We formulated our hypothesis based on data from nonschizophrenic patients, expecting to find that schizophrenic patients with obsessive-compulsive (OC) symptoms would experience more difficulties in the same cognitive areas as nonschizophrenic patients with obsessive-compulsive disorder (OCD). Patients had separate psychiatric and cognitive evaluations. The OC and non-OC schizophrenic subjects did not differ significantly on the positive and negative symptom scores. However, compared with non-OC schizophrenic patients, those with OC symptoms performed worse on cognitive areas thought to be impaired (i.e., visual-spatial skills, delayed nonverbal memory, and cognitive shifting abilities). In addition, the severity of OC scores correlated with poor performance in these areas of cognition. Our results support our hypothesis, specifically that OC symptoms may constitute a distinct cluster separate from psychosis in schizophrenia and raise the possibility of a distinct subtype of schizophrenia. The theoretical and clinical implications of these findings are discussed.

Differential relationships between positive and negative symptoms and neuropsychological deficits in schizophrenia

This study assessed the relationships between positive and negative clinical symptoms and specific neuropsychological deficits in a group of stable schizophrenic patients.

METHOD

Thirty patients were assessed using the Positive and Negative Syndrome Scale (PANSS) for schizophrenia and a battery of cognitive tests. The PANSS assessments were done by a group of raters blind to the results of cognitive tests, while the cognitive tests were conducted by a different group of raters who remained blind to the PANSS scores.

RESULTS

We found that, although positive and negative symptoms showed a trend toward direct correlation with each other, they correlated with distinct cognitive deficits. Patients with higher negative scores had more perseverative responses, perservative errors, and completed fewer categories on the Wisconsin Card Sorting Test; they also experienced more difficulties on trail making and verbal fluency tests. On the other hand, positive symptoms were associated with poor performance on the Digit Span, particularly the Digit Span Forward.

CONCLUSIONS

Our findings are in agreement with previous reports that negative symptoms may be associated with poor performance on cognitive tests reflecting particularly frontal function. Positive symptoms, on the other hand, seem to be associated with poor attention, specifically of auditory type, and thus, possibly with dysfunction within the more widespread neural networks underlying attention. Our findings support the hypothesis that positive and negative symptoms may be associated with distinct neuropsychological deficits and thus with distinct neurological substrates and point to the need to address both positive and negative dimensions when studying schizophrenia.

Adjunctive nadolol in the treatment of acutely aggressive schizophrenic patients

BACKGROUND

This study assessed the safety and efficacy of nadolol 120 mg/day compared with placebo, when administered adjunctively to neuroleptic in a group of acutely aggressive schizophrenic patients.

METHOD

Thirty-four male patients enrolled in this double-blind, placebo-controlled trial. The subjects were evaluated with the Brief Psychiatric Rating Scale (BPRS) and the Simpson Angus Neurologic Rating Scale for extrapyramidal effects. The total BPRS score as well as three factors, thought disturbance, hostility, and activation, was analyzed.

RESULTS

Compared with those who received placebo, the patients taking nadolol showed significant improvement on total BPRS score, particularly on the thought disturbance and activation factors, after the first treatment week (p = .05). By the end of the second treatment week, the patients taking placebo also began to show improvement, and the group differences were no longer significant. The patients treated with nadolol showed significantly more improvement on Simpson-Angus scores than those who received placebo (p = .03). However, there was no significant correlation between BPRS and Simpson-Angus changes. In the nadolol group, patients with and without akathisia showed no significant difference in their BPRS scores.

CONCLUSION

These findings suggest that adjunctive nadolol may be useful in the treatment of acutely aggressive schizophrenic patients by inducing a more rapid and consistent decrease of overall psychiatric symptoms and by reducing the extrapyramidal effects. Our results raise the possibility that the mechanism of action of nadolol on psychiatric symptoms in schizophrenic patients may be different from the mechanism of improvement of neuroleptic-induced extrapyramidal symptoms and akathisia. Nadolol may be a helpful adjunctive treatment for schizophrenic patients in general and not just for those with a high hostility level.

Thyromimetic mode of action of peroxisome proliferators: activation of 'malic' enzyme gene transcription

Peroxisome proliferators induce thyroid-hormone-dependent liver activities, e.g. 'malic' enzyme, mitochondrial glycerol-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, S14[Hertz, Aurbach, Hashimoto and Bar-Tana (1991) Biochem. J. 274, 745-751]. Here we report that the thyromimetic effect of peroxisome proliferators with respect to 'malic' enzyme result from transcriptional activation of the 'malic' enzyme gene, mediated by binding of the peroxisome proliferator activated receptor (PPAR alpha)/retinoid X receptor (RXR alpha) heterodimer to a 5'-flanking enhancer of the 'malic' enzyme promoter. The enhancer involved is distinct from the thyroid hormone response element of the 'malic' enzyme promoter and is partly homologous with that which mediates transcriptional activation of peroxisomal acyl-CoA oxidase by peroxisome proliferators. Hence transcriptional activation of thyroid-hormone-dependent liver genes by xenobiotic or endogenous amphipathic carboxylates collectively defined as peroxisome proliferators is mediated by a transduction pathway similar to that involved in transcriptional activation of peroxisomal beta-oxidative genes and distinct from that which mediates thyroid hormone action.

Activation of gene transcription by prostacyclin analogues is mediated by the peroxisome-proliferators-activated receptor (PPAR)

Xenobiotic amphipathic carboxylates, known collectively as hypolipidemic peroxisome proliferators (e.g., aryloxyalkanoic acids), or native long-chain fatty acids induce liver peroxisome proliferation and other biological activities. This broad spectrum of effects results from modulation of transcription of specific genes mediated by binding of peroxisome-proliferators-activated receptors (PPAR) to respective sequence-specific promoter elements (PPRE). The broad specificity and relatively low potency of reported hypolipidemic peroxisome proliferators prompted us to search for specific highly potent peroxisome proliferators. Here we report that stable prostacyclin analogues may act in such a manner. mPPAR alpha-mediated expression of a reporter gene linked to the peroxisomal rat acyl-CoA oxidase promoter was dose-dependently induced by carbaprostacyclin and iloprost. The ED50 for carbaprostacyclin was 25 nM, and carbaprostacyclin was therefore 25-fold and 200-fold more effective than the most potent xenobiotic (5,18,11,14-eicosatetraynoic acid) and native (arachidonic acid) inducers, respectively. Induction was further increased by cotransfecting the cells with mPPAR alpha and an expression vector for retinoic acid-X-receptor. PPAR-mediated activation of gene expression by prostacyclin analogues was specific for PPAR and was not observed using other members of the superfamily. No activation of gene expression was induced by other prostaglandins or leukotrienes at concentrations 100-fold higher than those of the prostacyclin analogues. Induction of gene expression by prostacyclin analogues was inhibited in cells transfected with the long-chain-acyl-CoA synthase, indicating that the acidic form of prostacyclin, rather than the respective CoA derivative or a metabolite derived thereof, serves as the activator of the PPAR/PPRE transduction pathway. Hence, PPAR-mediated modulation of gene transcription by prostacyclins may form the basis for their novel role as regulators of gene expression. Xenobiotic hypolipidemic peroxisome proliferators and native long-chain fatty acids seem to exploit the PPAR/PPRE transduction pathway used by prostacyclin.

Psychiatry Today : Biology vs. Psychology

This research addresses preferences and theoretical leanings of present-day psychiatrists along the continuum defined at one end by biology and at the other by psychology. A questionnaire was devised and sent to 5,702 randomly selected members of the American Psychiatric Association in 1990. The response rate was 307%. The results were analyzed for two groups: psychiatrists with fewer than 15 years of practice since residency and psychiatrists with more than 15 years of practice since graduation. Although the great majority of psychiatrists in both groups equally valued psychology and biology, the senior group attributed a greater importance to psychological methods, whereas the younger group stressed equally the importance of biology and psychology. This suggests that psychiatry has evolved over the years from a predominantly psychological practice to one with a more equal emphasis on psychology and biology. Recent advances in neuroscience may have shifted the pendulum toward a more balanced willingness of clinicians to consider the broad armamentarium of psychosocial and biological treatments. The results point to the need for further conceptualization into the relationship between biology and psychology and its incorporation into the psychiatric residency curriculum.

Treatment of obsessive-compulsive symptoms in schizophrenic patients with clomipramine

Recent studies show that obsessive-compulsive symptoms may occur in many patients with schizophrenia and may predict a poor prognosis. Pilot studies have shown that some schizophrenic patients may improve if a serotonin reuptake blocker is added to their neuroleptic. We have performed a pilot, double-blind, crossover study of clomipramine (CMI) or placebo, added to maintenance psychotropic medication. Six schizophrenic patients with obsessive-compulsive symptoms were studied in a double-blind CMI versus placebo crossover protocol. The patients met DSM-III-R criteria for chronic schizophrenia, experienced obsessive-compulsive symptoms, and had been previously stabilized on their psychiatric medication. The patients were rated at baseline and longitudinally through the study with the Positive and Negative Symptom Scale for Schizophrenia (PANSS) and the Yale Brown Obsessive-Compulsive Scale (YBOCS). An analysis of covariance was used to compare the drug versus placebo effect at the final visit with the baseline rating as a covariate. Ratings on both the YBOCS and the PANSS showed that patients improved significantly more on CMI than on placebo. No patients experienced an exacerbation of psychotic symptoms. Preliminary findings from this double-blind, crossover, pilot study of CMI and placebo, designed to assess the effect of CMI in the treatment of schizophrenic patients with obsessive symptoms, suggest that CMI is superior to placebo in the treatment of obsessions and compulsions and improves overall schizophrenic symptoms. Further studies with larger samples and longer follow-up period are necessary to confirm these preliminary findings.

Obsessive and compulsive symptoms in chronic schizophrenia

The goals of the study were to determine the prevalence of obsessive or compulsive (OC) symptoms among chronic schizophrenic patients, and to elucidate the level of function and course of illness in chronic schizophrenic patients with and without such symptoms. Therapists of 102 patients with DSM-III-R diagnoses of chronic schizophrenia reported on their patients' OC symptoms, level of function, and course of illness. Twenty-five percent of the chronic schizophrenic patients presented with significant OC symptoms. The OC schizophrenics had significantly earlier onsets of their illnesses, had spent more time in the hospital in the previous 5 years, and were judged by their therapists to have a lower level of capacity for age-appropriate function. In addition, such patients had been less often employed and less often married, and were more dependent on others. The poorer prognosis for schizophrenic patients with OC symptoms than for those without these symptoms suggests the need for new therapeutic strategies for such patients.

Clozapine following ECT: a two-step treatment

BACKGROUND

Some candidates for clozapine treatment may be unable to be given the drug. They may be so severely ill that they cannot or will not ingest a pill; their psychosis may have so compromised their physical status that use of clozapine, which produces a broad range of side effects, would be unsafe; and/or they may require a very rapid control of their behavior.

METHOD

Two case reports are described of patients who, although candidates for clozapine, were unable to take or be given the drug. Initial treatment with electroconvulsive therapy (ECT) was tried in both patients prior to use of clozapine.

RESULTS

In the two cases described, treatment with ECT prior to clozapine stabilized the patients enough that clozapine could be administered. In both cases, the clozapine appeared to perpetuate the initial clinical response produced by the ECT.

CONCLUSION

These case reports suggest that a two-step strategy of ECT followed by clozapine treatment may both facilitate the use of clozapine in some patients and perpetuate the clinical stability produced by ECT alone.

Transcriptional activation by amphipathic carboxylic peroxisomal proliferators is induced by the free acid rather than the acyl-CoA derivative

Most peroxisomal proliferators consist of a carboxylic group attached to a hydrophobic backbone yielding an amphipathic carboxylate molecule. The respective CoA derivatives of peroxisomal proliferators, formed by ATP-dependent CoA thioesterification catalyzed by long-chain-acyl-CoA synthase, have been repeatedly considered as the immediate inducers of peroxisome and other genes. In this study, the putative requirement for prior CoA thioesterification of peroxisomal proliferators was evaluated by analyzing the induced expression of a reporter plasmid promoted by the peroxisomal acyl-CoA-oxidase promoter in cells transiently cotransfected with expression vectors for the peroxisome-proliferator-activated receptor and the long-chain-acyl-CoA synthase. Transcriptional activation of peroxisomal acyl-CoA oxidase by peroxisomal proliferators was inhibited in the presence of transfected functional acyl-CoA synthase. The inhibitory effect was negatively correlated with the capacity of the acyl-CoA synthase to catalyze CoA thioesterification of the respective proliferator. Hence, the immediate inducer is the peroxisomal proliferator free acid rather than the respective CoA derivative or a metabolite derived from the peroxisomal-proliferator-CoA intermediate.

Morphometric mapping of regional myocyte diameters after healing of myocardial infarction in cats

Myocyte diameters were measured in two models of healed myocardial infarction to test the hypothesis that myocyte hypertrophy is a function of proximity to the infarct. Left ventricular transmural and non-transmural myocardial infarctions were produced in cats by multiple ligatures of the distal tributaries of the left coronary artery system. Thirteen to twenty months after surgery the left ventricular free wall was cut longitudinally, embedded in plastic and stained for reticulum with modified silver stain. Myocardial cell diameters were measured from apex to base through the infarct. No regional differences were found in non-operated control hearts. In the transmural infarct hearts, all cell diameters were significantly increased in comparison to controls (P less than or equal to 0.05). In the hearts with non-transmural infarcts, cell diameters were significantly increased in tissues adjacent to the infarct, but as distance from the infarct increased the cell diameters were not different from controls. Cells from the transmural infarctions had a greater percent increase in diameter, compared to controls, than did cells from the non-transmural infarctions. There is a gradient increase in myocyte diameters in transmural and non-transmural healed myocardial infarctions; this increase is greatest in the tissues adjacent to the infarct. We conclude that cells close to a healed myocardial infarction hypertrophy because they are contracting against a non-compliant scar.

Kinetics of proteoglycans and cells in growth plate of normal, diabetic, and malnourished rats

The metabolism of proteoglycans in normal growth plate and the changes in growth plate morphology induced by diabetes and malnutrition were studied in rats. The proteoglycans had a significantly faster turnover (half-life measured with [35S]sulfate labeling: 25-30 h) than the cells in the growth plate. Morphometric studies showed significant reductions of cell number, zone height, and [3H]thymidine incorporation in growth plates from rats with untreated streptozotocin-induced diabetes compared to normal rats. Similar, although less pronounced alterations were observed in malnourished, nondiabetic rats. Disaggregation and degradation of proteoglycans are probably necessary prerequisites for calcification. Our data indicate that the proteoglycans are in a dynamic state of rapid biosynthesis and degradation throughout the growth plate with a shift in the balance at the calcification front toward less synthesis and more degradation.

Localization of collagenase in the growth plate of rachitic rats

In the transition from proliferation to hypertrophic cell zones in the growth plate, there is an increase in chondrocyte volume and a corresponding decrease in collagen content to accommodate the enlarging cells. It is postulated that collagenase accounts for this collagen loss. To test this hypothesis, tibial growth plates were obtained from normal rats, rachitic rats deficient in vitamin D and phosphate, and rats after 48 and 72 h of healing from rickets. Collagenase was quantitated by a pellet assay based on the release of solubilized collagen from the endogenous insoluble collagen in the tissue homogenates. A fourfold greater collagen release and a concomitant sixfold greater hypertrophic cell volume were measured in rachitic growth plates compared with normal age-matched controls. During healing of rickets, collagenase activity and hypertrophic cell volume returned almost to control levels. Rachitic growth plates were dissected into the juxtaepiphyseal 1/3 and the juxtametaphyseal 2/3. The latter portion contained greater than 95% of the hypertrophic cells and 86% of the collagenase. The collagen-degrading activity was extracted from this region and was shown to be a true collagenase by its production of typical A fragments of tropocollagen produced by collagenase action. The enzyme was activated by aminophenylmercuric acetate and trypsin and was inhibited by EDTA, 1,10-phenanthroline, and a tissue inhibitor of metalloproteinases from human articular cartilage. Inhibitors of aspartic, cysteine, and serine proteases had no effect. Micropuncture fluids aspirated from rachitic cartilage contained latent collagenase activity, indicating an extracellular localization. Negative tests for hemoglobin in the rachitic cartilage samples indicated that there was no contamination by capillaries and that this was not a source of collagenase. It is concluded that extracellular collagenase accounts for the loss of cartilage matrix in the hypertrophic zone, and that this process may be distinct from that of capillary invasion.

Proteoglycans from rabbit articular and growth plate cartilage. Ultracentrifugation, gel chromatography, and electron microscopy

Proteoglycans are considered to be important for the mechanical properties of articular cartilage and growth plate and for the regulation of calcification of growth plate. We have used ultracentrifugation, gel chromatography, and electron microscopy to characterize and compare proteoglycans isolated from rabbit articular cartilage, uncalcified growth plate, and calcified cartilage. We found that proteoglycans from articular cartilage were more resistant to extraction than were proteoglycans from uncalcified growth plate and calcified cartilage. Long term neutral decalcification of calcified cartilage resulted in degraded proteoglycans. The chondroitin sulfate chains from all three tissues had similar size distribution. Gel chromatography and electron microscopy of proteoglycan monomers suggested that those from uncalcified growth plate were largest, those from articular cartilage intermediate, and those from calcified cartilage smallest. Proteoglycan aggregates from articular cartilage were longer than those from uncalcified growth plate. Both biochemical and quantitative electron microscopic data suggested the existence in mineralizing cartilage of at least two different sized populations of proteoglycan aggregates.

Role of kidney in the catabolic clearance of human platelet antiheparin proteins from rat circulation

Stimulated platelets release at least two antiheparin proteins: platelet factor 4 (PF4) and low affinity platelet factor 4 (LA-PF4) from which beta-thromboglobulin (beta TG) is derived. We have found previously marked elevation of LA-PF4/beta TG antigen in platelet poor plasma of patients with chronic renal failure, whereas levels of PF4 remained normal. Therefore, we examined the role of the kidneys in the metabolic clearance of LA-PF4/beta TG and PF4. The supernates of aggregates of thrombin-stimulated human platelets were injected into sham operated control rats, nephrectomized rats, and into rats with acute ureteral ligation. The disappearance of human LA-PF4/beta TG antigen and PF4 in rat plasma determined by specific radioimmunoassays followed biphasic exponential curves. The half-lives (t1/2) for the fast and slow components of LA-PF4 in control rats were 6.4 and 68.4 min. Nephrectomy significantly increased these times to 9.7 and 144 min, while ureteral ligation resulted in no significant change. Comparison of the level of LA-PF4/beta TG antigen and of creatinine in aorta and in renal vein showed 25%-30% extraction of these compounds by the kidney. Less than 0.1% of the total LA-PF4 antigen injected was recovered in the urine of control rats. In contrast to these results, the clearance of PF4 was not affected by nephrectomy.

IN CONCLUSION

(1) functional renal tissue is necessary for normal clearance of LA-PF4/beta TG, but renal excretion does not play a major role in its elimination suggesting that the protein is catabolized by the kidney; and (2) catabolic clearance of PF4 does not depend on functioning kidney tissue.

Characterization of intracellular viral RNA in interferon-treated cells chronically infected with murine leukemia virus

We have recently found that Moloney murine leukemia virus assembles within cytoplasmic vacuoles of chronically infected NIH/3T3 cells rather than at their surface (submitted for publication). In the present study we found that if these cells were treated with interferon (IF) for 24 to 48 h the intracellular virus particles accumulated at a two- to threefold-higher level than that observed in untreated cells. Nevertheless, despite this accumulation, no difference between IF-treated and untreated cells was observed in the amount of the total cytoplasmic viral RNA or in its 35S or 21S species. When cellular virions were sedimented from the cytoplasmic fraction, a markedly higher amount of viral RNA was detected in the viral pellet of IF-treated cells than was detected in untreated cells, whereas the amount of viral RNA left in the virus-free cytoplasm of IF-treated cells was much lower than that in the untreated cells. Furthermore, the amount of the cytoplasmic polyriboadenylic acid-containing viral RNA was also remarkably higher in the IF-treated cells. Viral polyribosomes appeared to be fully functional in IF-treated cells, since no effect of IF on viral protein synthesis could be detected. Analysis of the nuclear viral RNA showed no difference between IF-treated and untreated cells after 24 h of IF treatment. Both contained a comparable amount of 35S viral RNA. However, at 48 h a significant accumulation of viral RNA was observed in the nucleus of the IF-treated cells as compared with the untreated cells, although in both cases only 35S species were evident. This accumulation appeared to activate a degradation process which destroyed nuclear viral RNA, since a dramatic shift toward smaller-sized molecules of viral RNA and a remarkable reduction in its amount were observed after 72 h of IF treatment.

Secreted platelet proteins with antiheparin and mitogenic activities in chronic renal failure

The levels of secreted platelet antigen (LA-PF4/beta TG) were measured by radioimmunoassay in samples of PPP obtained from human blood collected on EDTA and inhibitors of platelet release reaction. These levels in plasma of 17 normal individuals, 18 nondialyzed patients with chronic renal failure, and nine patients on hemodialysis were 31.9 +/- 2.8 ng/ml, 135.1 +/- 21.4, and 291.8 +/- 26.3, respectively. No significant differences were observed in platelet counts and in the levels of this antigen in PRP of these three groups of individuals. The levels of PF4 in PPP of eight normal individuals and in plasma of seven patients with chronic renal failure were 7.41 +/- 0.67 and 7.53 +/- 1.11 ng/ml, respectively. During processing of blood samples in the absence of platelet release inhibitors, platelets of patients with chronic renal failure released less LA-PF4/beta TG antigen than did normal platelets. The mean levels of LA-PF4/beta TG antigen excreted in urine of six normal individuals and 10 patients with chronic renal failure were 57.75 and 1461.5 ng/100 mg of creatinine per day, respectively. After 3 hr hemodialysis, LA-PF4/beta TG antigen levels in PPP increased from 291.8 +/- 26.3 ng/ml to 505.3 +/- 87.3. By contrast, this antigen in three patients with successful kidney transplants rapidly returned to levels close to normal following graft function. Immunoreactive material from pooled urine of patients with chronic renal failure was isolated by isoelectric focusing. This material focused at pH 10.0 to 10.8 and induced DNA biosynthesis in 3(3 swiss cells, indicating its similarity to PBP. It is proposed that elevation of LA-PF4/beta TG antigen observed in plasma of patients with chronic renal failure resulted from the impaired handling of this protein by the kidney.

Increased Levels of Low Affinity Platelet Factor 4 in Plasma and Urine of Patients With Chronic Renal Failure

Low affinity platelet factor 4 (LA-PF4) is a specific platelet secretory protein immunologically related to β-thromboglobulin and to platelet basic protein that stimulates cell growth. The level of LA-PF4 antigen was determined by specific radioimmunoassay in platelet poor plasma (PPP) and platelet rich plasma (PRP) of 17 normal individuals (NI), 9 patients on hemodialysis (HD) and 18 patients with chronic renal failure (CRF) who were not dialysed. Eight patients with glomerular filtration rate (GFR) 5-20 ml/min were included to group 1 and 10 patients with GFR 30-50 ml/min were included to group 2. Levels of LA-PF4 in ng/ml PPP were 31.9 ± 2.8 in NI, 291.8 ± 26.3 in HD, 149.4 ± 45.2 in group 1 of CRF and 103.7 ± 11.1 in group 2 of CRF. Differences between patients and NI were significant at P <0.05. After 3 hours of hemodialysis LA-PF4 increased to 505.0 ± 92.3 (P < 0.05), however, there was no changes in PPP level across the artifical kidney at one hour. The levels of LA-PF4 in PRP of patients with CRF and HD did not differ from NI. Mean LA-PF4 excretion in urine (ng/day/100mg creatinine) was 57.7 ± 6.4 (range 33.3-75.7) in 6 NI with GFR >60 ml/min and 1461.5 ± 674.6 (range 105.3-7041.6) in 10 CRF patients. In conclusion, elevation of LA-PF4 in PPP of patients with CRF and its increased urinary excretion suggest stimulation of platelet secretion and/or decreased metabolism of LA-PF4 in the kidney.

Biosynthetic and structural studies of hemoglobin in a patient with congenital dyserythropoietic anemia type I

A 25 year old woman with congenital dyserythropoietic anemia (CDA) Type I is described. Typical morphologic abnormalities of the erythroid precursors in the bone marrow by light and electron microscopy, marked ineffective erythropoiesis and iron loading were present, Globin chain synthetic ratios as well as functional and structural studies on the patients hemoglobin were normal, ruling out the presence of thalassemia or a mutant hemoglobin which can both give rise to morphologic and clinical features similar to CDA. The laboratory findings on this patient and family members and a brief review of the literature are presented.

An autoradiographic and morphological study of mouse bone marrow littoral cells during and after treatment with urethane

This study demonstrates that the labeling index of mouse marrow littoral cells can be markedly altered as a result of treatment with ethyl carbamate (urethane). Young C57/BL mice were given daily intraperitoneal urethane injections for periods up to 6 days. Following treatment each day, as well as daily over a 10 day recovery period, a group of animals was administered tritiated thymidine every 3 hr over a 24 hr period and sacrificed 1/2 hr after the last injection. Marrow was embedded in epon and 0-5 mum sections cut for autoradiographic and light microscopic analysis. A thirty-five-fold increase in the percentage labeled littoral cells was observed after three injections of urethane. The labeling index of littoral cells fluctuated during the treatment period and during the 10 day recovery period. The albeling data are discussed in relation to the possible effects of urethane on the cell cycle of mouse marrow littoral cells; the morphological sequela to urethane treatment and the possibility that littoral cells may act as stem cells.