[Surgical removal of large cavernous angioma in the pontomedullary junction: a case report]

Recent advances in neuroradiology have enabled us to approach cavernous angioma in the brain stem. A case of large cavernous angioma, which was located in the pontomedullary junction, was removed surgically. A 24-year-old female was admitted with occipitalgia, dizziness, nausea, gait disturbance. On neurologic examination, the patient had right hemiparesis, slight right facial palsy and paresthesia, right hemiparesthesia, dysphagia. T1 weighted Gd enhanced MRI revealed a mixed intensity lesion. These findings were thought to be consistent with a cavernous angioma. Follow up MRI findings demonstrated progressive increase in cavernous angioma. Vertebral angiograms showed a mass sign and a venous angioma in the midline of the pontomedullary junction. Therefore, the operation was performed in an attempt to remove the cavernous angioma through the midline of the fouth ventricle. The operation was performed under monitoring of electromyogram of facial muscle and external ocular muscle. The cavernous angioma was removed totally, and addition neurogical deficits were minimal.

Human trabecular meshwork cells as a thyroid hormone target tissue: presence of functional thyroid hormone receptors

PURPOSE

To determine whether human trabecular meshwork cells (HTM) are a potential target tissue for thyroid hormone (3,3',5-triiodothyronine, T3).

METHODS

Cultured HTM were assayed for the presence of thyroid hormone receptors (TRs) and retinoid X receptors (RXRs) by reverse-transcriptase polymerase chain reaction (RT-PCR) to detected TR and RXR mRNA, and by immunohistochemistry to detect nuclear TR and RXR proteins. Functionality of the TR was determined by analysis of 125I-T3 binding affinity and capacity in HTM nuclear extracts. Effects of T3 on modulation of hyaluronic acid (HA) levels in HTM were measured as a function of dose and duration of T3 administration.

RESULTS

Analysis of RT-PCR and immunohistochemistry demonstrated that cultured HTM expressed TRalpha1, TRalpha2, and TRbeta1 but not TRbeta2; and RXRalpha but not RXRbeta and RXRgamma isoforms. Saturation binding and analysis of 125I-T3 to HTM nuclear extracts revealed Kd of 57 pM. The number of T3 binding sites extrapolated from a Scatchard plot was 7.3 x 10(10)/microg of HTM nuclear protein extract. T3 supplementation reduced the concentration of HA in the cell medium by 32-43% compared to cells grown in the absence of T3.

CONCLUSIONS

Cultured HTM express three TR isoforms and one RXR isoform, bind T3 with an affinity similar to that of TR in responsive cells, and modulate their HA production in response to T3. These findings indicate that the human trabecular meshwork tissue has the capacity to respond to thyroid hormones.

Atrial natriuretic peptide as a preload depressor in acute renal failure secondary to congestive heart failure

The present study was undertaken to verify the hypothesis that infusion of atrial natriuretic peptide (ANP) might lower preload and be beneficial in the treatment of pulmonary congestion even without a diuresis in patients with acute renal failure (ARF) secondary to severe congestive heart failure (CHF). We studied 22 patients with ARF secondary to CHF. The mean age of the patients (14 men and 8 women) was 72 years (range 36 to 85 years). Seven of the patients had dilated cardiomyopathy, ten had ischemic heart disease, and five had valvular heart disease. ANP was infused intravenously and the following data before and 1 hour after the start of ANP infusion were recorded; urinary output, systemic blood pressure (SBP), pulmonary blood pressure (PBP), right atrial pressure (RAP), cardiac index (CI), heart rate (HR), and arterial blood oxygen partial pressure. Diastolic PBP were employed as pulmonary capillary wedge pressure. Urinary output did not change. Mean SBP decreased from 92 to 85 mmHg (p < 0.05), and mean PBP decreased from 34 to 28 mmHg (p < 0.01). Mean RAP decreased from 11 to 9 mmHg (p < 0.01) and diastolic PBP decreased from 25 to 19 mmHg (p < 0.01). HR did not change significantly and CI increased 2.4 to 2.5 mi/min/m2 (p < 0.05). Arterial blood oxygen partial pressure increased significantly from 71 to 82 mmHg (p < 0.05). In conclusion, ANP decreased preload and improved arterial blood oxygen partial pressure, though diuretic response to ANP is attenuated in ARF secondary to CHE. Infusion of ANP will be very beneficial in cases in which dyspnea and pulmonary edema due to elevation of preload are the principal clinical problems.

Human parvovirus B19 infection resembling systemic lupus erythematosus

A 39-year-old female visited our hospital because of morning stiffness, arthralgia, skin rash of the extremities and general fatigue. On examination, she also had a malar rash and an oral ulcer. Laboratory findings revealed that antinuclear antibodies were positive and complement component levels (C3, C4, CH50) were all low. Serology for human parvovirus B19 (HPV-B19) was positive for both immunoglobulin (Ig)M and IgG. Gradually, her symptoms improved and laboratory data returned to normal range without medications. This case suggests that HPV-B19 infection may be attributed to the pathogenesis of systemic lupus erythematosus.

Mutations in the E-domain of RAR portion of the PML/RAR chimeric gene may confer clinical resistance to all-trans retinoic acid in acute promyelocytic leukemia

The binding of all-trans retinoic acid (ATRA) to the ligand-binding region in the E-domain of retinoic acid receptor-alpha modifies the transcriptional activity of RARalpha protein. ATRA probably induces differentiation of acute promyelocytic leukemia (APL) cells by binding to the E-domain of the RARalpha portion (RARalpha /E-domain) of PML/RARalpha chimeric protein. Therefore, molecular alteration in the RARalpha /E-domain of the chimeric gene is one mechanism by which patients with APL may acquire resistance to ATRA therapy. In this study using reverse transcription-polymerase chain reaction and single-strand conformation polymorphism, DNA segments amplified from the RARalpha /E-domain in fresh APL cells of 23 APL patients (8 males and 15 females from 4 to 76 years of age) were screened for mutations. Of those patients, 3 patients (1 with de novo and 2 with relapse) had clinical resistance to ATRA therapy. We found mutations in the RARalpha /E-domain of PML/RARalpha chimeric gene exclusively in the 2 patients who exhibited ATRA-resistance at relapse, whereas the mutations were not detected at their initial onset. Interestingly, these patients received a prolonged or intermittent administration of ATRA before relapse with ATRA-resistance. The mutations lead to the change of amino acid in the ligand-binding region of RARalpha /E-domain, Arg272Gln, or Met297Leu according to the amino acid sequence of RARalpha, respectively. Further study demonstrated that the in vitro ligand-dependent transcriptional activity of the mutant PML/RARalpha protein was significantly decreased as compared with that of wild-type PML/RARalpha. These findings suggest that mutations in the RARalpha /E-domain of the PML/RARalpha chimeric gene may confer clinical resistance to ATRA therapy in patients with APL.

Characterization of mouse retinoid X receptor (RXR)-beta gene promoter: negative regulation by tumor necrosis factor (TNF)-alpha

A genomic clone of mouse retinoid X receptor (RXR)-beta (Rxrb) has recently been isolated and mapped within the H2-K region of the mouse major histocompatibility complex. A putative 250-bp promoter, which is located between Rxrb and H2-Ke4, and may possibly be their common promoter, has also been identified. In order to study the gene regulation of Rxrb, we analyzed the transcriptional function of the Rxrb promoter with chimeric constructs containing the Rxrb promoter fragments fused upstream of a firefly luciferase cDNA, which were transiently transfected into rat GH3 cells. We found that 1) a part of the H2-Ke4 genomic region (1.9-kb), as well as the 250-bp promoter, was transcriptionally active as an Rxrb promoter; 2) tumor necrosis factor (TNF)-alpha significantly repressed the activity of the 250-bp promoter although thyroid hormone, 9-cis retinoic acid, interleukin (IL)-1beta, and IL-6 did not affect the activity; 3) either the change in orientation or point mutations of a consensus NF-kappaB site located in the 250-bp promoter did not affect the repression; 4) SB 203580, a highly specific inhibitor of p38 mitogen-activated protein (MAP) kinase, completely abolished the repression by TNF-alpha. These data suggest that TNF-alpha represses the promoter activity of the 250-bp region, and the repression is mediated by p38 MAP kinase independent of NF-kappaB. We thus have first shown a relation between the retinoic acid receptor and a cytokine TNF-alpha.

Structure and transcriptional function of the 5'-flanking region of rat thromboxane receptor gene

We cloned a cDNA for rat TX receptor, and observed its expression in the kidney, including vascular smooth muscle. The aim of the present study was to clone the 5'-flanking region (5'-FL) of rat TX receptor gene, and to examine its transcriptional gene expression regulation. The 5'-FL was cloned by a PCR method, and the nucleic acid structure of 5'-FL (approximately 1 Kb) was disclosed. The transcription initiation site was shown to be 63 bases upstream of the 5' end of the cDNA by the primer extension. In the 5'-FL, putative AP-1 binding sites, glucocorticoid-responsive elements, NF-kappa B binding sites, GATA box, and shear stress-responsive elements were identified. The 5'-FL was then fused upstream of firefly luciferase cDNA in an expression vector, and we examined its transcriptional activity in transiently transfected cultured vascular smooth muscle cells (VSMC). Luciferase expression was dependent on the length of 5'-FL, and it was significantly stimulated by phorbol 12-myristate 13-acetate (PMA), dexamethasone (Dex), tumor necrosis factor-alpha, and interleukin (IL). By a semi-quantitative RT-PCR method, TX receptor mRNA was shown to be induced by Dex, IL-6, and PMA in cultured VSMC. In conclusion, we have revealed the structure of transcription regulatory region of TX receptor. Expression of TX receptor gene is possibly up-regulated by activation of protein kinase C, glucocorticoid excess, and IL-6, in vascular smooth muscle.

[Traditional remedy-induced Chinese herbs nephropathy showing rapid deterioration of renal function]

A 19-year-old female was referred to our hospital for azotemia and anemia. She had been taking a health food for atopic dermatitis for about three years. Urinalysis showed proteinuria, glycosuria and microscopic hematuria. Generalized aminoaciduria was observed. Moreover, severe anemia, azotemia, hypokalemia and hypophosphatemia were also observed. Renal biopsy specimen disclosed hypocellular interstitial fibrosis and degeneration of the proximal tubular epithelial cells. No remarkable changes were observed in the glomeruli. Aristolochic acid was detected in the health food. From these findings, she was diagnosed as having Chinese herbs nephropathy (CHN). Although consumption of the food intake was stopped, her renal function deteriorated rapidly. Previously, we reported that certain kinds of Chinese herbal drugs contain aristolochic acid and that the drugs should be prohibited if aristolochic acid is identified. However, we experienced a patient of CHN arising from traditional remedy, which was not proved to be safe. It should be awared that health foods may contain aristolochic acid.

Kidney-specific expression of a novel mouse organic cation transporter-like protein

Using the signal sequence trap method, we have cloned a novel 12-membrane-spanning transporter-like protein, termed renal-specific transporter (RST), from the mouse kidney. RST is a 553-amino-acid protein highly homologous to recently cloned organic cation transporters, e.g. it is 30% identical to rat organic cation transporter I at the amino acid level. Northern blot analysis has revealed that the RST gene is expressed abundantly and specifically in the kidney. In situ hybridization analysis has shown that RST gene expression is restricted to the renal proximal tubule, where various organic cations such as endogenous catecholamines and choline or clinically used cationic drugs are known to be actively excreted.

Growth-dependent induction of angiotensin II type 2 receptor in rat mesangial cells

Angiotensin II acts on at least two receptor subtypes, AT1 and AT2. Although the physiological role of the AT2 receptor is still poorly defined, it may be implicated in inhibition of cell growth, vasorelaxation, and apoptosis. In the present study, to investigate the role of the AT2 receptor in the kidney and its implication in hypertensive states, we examined its expression using cultured mesangial cells (MC) from normotensive Wistar-Kyoto rats (WKY) and from stroke-prone spontaneously hypertensive rats (SHRSP). Receptor binding assays were performed using a nonselective ligand, [Sar1,Ile8]angiotensin II, or AT2-selective CGP42112A. Binding assays revealed that MC from WKY exhibited both AT1 and AT2 receptors, the ratio of which was confluence-dependent. In contrast, MC from SHRSP, whose proliferation activity was much higher than those from WKY, showed only the AT1 subtype. In receptor binding and Northern blot analyses, expression of the AT2 receptor of WKY-MC was low in the growing state but significantly induced upon confluence to become abundant in the post-confluent state, whereas that of SHRSP-MC was undetectable in either state. Gene expressions of AT1A and AT1B receptors were not significantly altered in either strain during the time in culture. These results indicate that the mesangial AT2-receptor expression is growth-dependent and suggest a role in the inhibition of MC growth in WKY. Much lower expression of the AT2 receptor in MC from SHRSP may suggest involvement in their higher proliferation activity and possibly in consequent renal disorders.

Isolation and characterization of nickel-accumulating yeasts

We selected three yeast strains that efficiently remove heavy metal ions from aqueous solution. We first screened yeasts that grew in the presence of 2 mM NiCl2 among our stock of wild yeasts, and then selected those that removed Ni most efficiently from aqueous solution. These strains also removed Cu and Zn from aqueous solution and were identified as Candida species. Ni uptake was efficient at pH between 4.0 and 7.0, but less efficient at pH below 3.0. The amount of Ni taken up by the yeast cells was proportional to the initial concentration of NiCl2 below about 4 mM Ni. The cells retained the abilities to remove Ni after treatment with 10 mM EDTA or 1 M HCl for repeated usage, or after heat treatment.

Retinoid X receptors in the kidney: their protein expression and functional significance

Retinoid X receptors (RXRs) heterodimerize with 1,25-dihydroxyvitamin D3 (VD) receptor (VDR), and play important roles in VD-regulated transactivation. VD acts on many tissues including kidney for the regulation of calcium homeostasis. In the kidney, the expression of VDR in the tubular cells has been well studied. In contrast, little is known about the localization and the functional significance of RXRs there. In order to elucidate these questions, we first performed immunohistochemical analyses of rat kidney using isoform-specific antimouse RXR antibodies we have previously reported. Interestingly, all RXR isoforms, predominantly RXR alpha, mainly localized to the proximal and the distal tubules, but not to the glomeruli. The serial section staining using anti-VDR antibody showed the colocalization of RXR alpha and VDR in those tubular cells. In order to elucidate the functional significance of endogenous receptors in the tubular cells, we next performed transient transfection studies using the tubular-cell derived Madin-Darby bovine kidney cells, which express both endogenous VDR and RXR. We transfected a reporter plasmid containing direct repeat 3 (DR3) sequence, to which only RXR/VDR heterodimer can bind, and found that VD and 9-cis retinoic acid, as well as VD and RXR selective agonist LG100153, had an additive effect for the DR3 transactivation. Taken together, we speculate that endogenous RXRs co-localize with VDR, and coregulate VD-dependent genes in the tubular cells of the kidney as RXR/VDR heterodimer.

A 41-year-old woman with protein S deficiency and diffuse proliferative lupus nephritis: is protein S deficiency associated with a hyperinflammatory response?

A 41-year-old woman with complete protein S (PS) deficiency who developed diffuse proliferative lupus nephritis is reported. She was referred to our hospital with nephrotic syndrome and thrombocytopenia. Her medical history included colorectostomy and amputation of the extremities because of repeated thrombotic episodes during her teens without any evidence of systemic lupus erythematosus. The diagnosis of PS deficiency was made from the patient's clinical course, undetectable serum PS in either the active or inactive form, normal protein C activity, and no evidence of the antiphospholipid syndrome. However, there was no definitive family history. A depressed level of complements and a positive antinuclear acid antibody suggested a diagnosis of systemic lupus erythematosus. The patient had a rapidly progressive course and died of disseminated intravascular coagulation. An autopsy showed generalized thrombotic lesions and diffuse proliferative lupus nephritis on both ordinal light and immunoperoxidase microscopy. Our observations suggest that PS-deficient patients may have a hyperinflammatory response.

[Chinese herbs nephropathy in the Kansai area: a warning report]

In 1993, Vanherweghem and his associates reported cases of rapidly progressive renal interstitial fibrosis in young women who were administered a slimming regimen including Chinese herbs. Subsequently, similar cases have been reported. In Japan, especially in the Kansai area, several cases of Chinese herbs nephropathy have already been reported. We experienced a patient suffering from Chinese herbs nephropathy (CHN), and further detected aristolochic acids from the Chinese herbs taken by the patient. Aristolochic acids are known to be causative agents of CHN. The danger of CHN should be noted as soon as possible and drugs containing aristolochic acids should be prohibited.

Immunohistochemical expression of retinoid X receptor isoforms in human pituitaries and pituitary adenomas

Retinoid X receptors (RXRs) are transcriptional factors that belong to the steroid/thyroid hormone receptor superfamily. There are 3 RXR isoforms-alpha, beta, gamma-known to bind 9-cis-retinoic acid as their ligand. The expression of RXRs in human pituitary glands and pituitary adenomas has not been extensively investigated. To determine whether specific RXR isoforms may play roles in the state of differentiation of pituitary adenomas, we have investigated the immunohistochemical expression of RXR alpha and RXR gamma in 6 nontumorous pituitaries and in 60 different pituitary adenomas using isoform-specific antibodies. In the nontumorous pituitaries. RXR alpha was expressed in the nuclei of almost all cells, while RXR gamma was only expressed in thyrotropin (TSH) cells and in some cells positive for growth hormone (GH) and glycoprotein alpha-subunit (alpha SU) but not in luteinizing hormone (LH) beta-subunit, follicle-stimulating hormone (FSH) beta-subunit, prolactin (PRL) or adrenocorticotropin (ACTH) cells by double immunostaining. All 60 adenomas were RXR alpha positive, and 39 of 60 adenomas (65%) were positive for RXR gamma. The incidence of RXR gamma immunoreactivity in the different adenoma types was: 13 of 16 GH-producing adenomas (81.3%), 9 of 14 PRL-secreting adenomas (64.3%), 6 of 6 TSH-secreting adenomas (100%), 2 of 5 ACTH-secreting adenomas (40%) and 9 of 19 nonfunctioning adenomas (47.4%) including immunohistochemically gonadotropin-subunit-positive adenomas. The colocalization of RXR gamma with the TSH beta subunit, GH and alpha SU in the same adenoma cells was frequently observed, and sometimes RXR gamma was colocalized with PRL, ACTH, FSH beta or LH beta as shown by double immunostaining. We conclude that RXR alpha is expressed in both human pituitaries and pituitary adenomas. In contrast, RXR gamma is expressed more broadly in pituitary adenomas than in normal pituitaries and thus may play a role in the differentiation-specific cell types in the human pituitary both under physiological and pathological conditions.

Immunolocalization of rat thromboxane receptor in the kidney

Thromboxane (TX) is a vasoactive hormone which is known to be involved in renal physiology and pathophysiology. To identify the site of action of TX in the kidney, we examined the distribution of this receptor in the normal rat kidney using a polyclonal antibody against TX receptor we had raised. Western immunoblot of rat kidney membrane fractions with the antibody identified a single protein band at the predicted molecular mass of rat TX receptor protein. In the rat kidney, immunostainable TX receptor was observed in glomeruli, arterial walls, luminal membranes of thick ascending limbs of Henle's loop, the luminal and basolateral membranes of either distal convoluted tubules or connecting tubules, and the basolateral membranes of collecting tubules. The localization of TX receptor provides better understanding of the mechanism of previously reported effects of TX on glomerular and tubular functions leading to hypertension as well as renal parenchymal diseases.

[A case of fluminant septic shock due to Streptococcus agalactiae in a patient with MPO-ANCA related glomerulonephritis]

Recently group A Streptococcus toxic shock like syndrome (TSLS) has been reported, but as for group B streptococcus (S. agalactiae) infection, there have been little documentation in the literature. We report a case of fluminant septic shock due to Streptococcus agalactiae (S. agalactiae). A 72-year-old male was admitted to our hospital because of general fatigue and azotemia. He was diagnosed as having MPO-ANCA related glomerulonephritis and treated with steroid therapy. Gradually he was doing well. On the 228th hospital day, he suddenly had tachypnea, transient conscious disturbance, and profound hypotension. About 16 hours later, he died despite intensive treatment. S. agalactiae was isolated from the blood. Autopsy revealed bilateral bronchopneumonia and shock liver. To our knowledge, this is the first report of septic shock caused by S. agalactiae.

Dosage effects of the three Wx genes on amylose synthesis in wheat endosperm

Amylose synthesis in wheat endosperm is mainly controlled by the granule-bound starch synthase of about 60 kDa, the so-called waxy (Wx) protein. The Wx proteins are the product of the Wx genes at a triplicate set of single-copy homoeoloci located on chromosomes 7A (Wx-A1), 4A (Wx-B1) and 7D (Wx-D1). Using 'Chinese Spring' and its aneuploid lines, including nullisomic-tetrasomics, tetrasomics, ditelosomics and deletion stocks, together with single-chromosome substitution lines for these chromosomes, the effects of varying the dosage of whole chromosomes and chromosome arms, as well as the effects of null alleles, upon amylose synthesis were investigated. Nullisomic 4A and the deletion of chromosome segments carrying the Wx-B1 gene reduced the amylose content by more than 3%. A reasonable agreement was found in the substitution lines. This confirms that the absence of the Wx-B1 gene, or else substitution of this gene by its null allele, has the most striking effect on decreasing amylose synthesis. The removal of chromosomes carrying either the Wx-A1 or the Wx-D1 gene reduces the amylose content by less than 2%. A similar reduction was revealed by substitution of these two genes by the null alleles. Double dosages of chromosomes 7A, 4A and 7D did not increase amylose content, while the tetrasomic chromosomes produced more of the respective Wx proteins. This suggests that a certain level of Wx gene activity or of the Wx proteins led to the maximum amount of amylose.

C-type natriuretic peptide in chronic renal failure and its action in humans

We have previously reported that C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family, is produced in vascular endothelial cells and acts as an endothelium-derived relaxing peptide. To clarify the clinical significance of CNP in renal disorders, we examined the plasma level of CNP in patients with various cardiovascular diseases, including chronic renal failure (CRF) patients who were under hemodialysis therapy. We also investigated biological effects of intravenously-administered CNP (0.43 nmol/kg) by bolus injection from the peripheral vein in healthy volunteers and measured systemic hemodynamic variables, plasma levels of CNP, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), cGMP, aldosterone and also urine volume, urinary excretions of sodium, potassium, chloride and cGMP. The plasma CNP levels in healthy humans (N = 13) was 1.4 +/- 0.6 fmol/ml. In CRF patients, the plasma CNP significantly increased up to 3.0 +/- 1.1 fmol/ml. The administration of CNP elicited significant increase of plasma cGMP level (from 4.77 +/- 1.25 to 8.33 +/- 1.59 pmol/ml 15 min after the administration) and of urinary cGMP excretion (from 30.7 +/- 4.3 to 74.9 +/- 13.4 nmol/30 min). Intravenously-administered CNP exerted significant diuretic (% increase: +117 +/- 85.0), natriuretic, kalliuretic and chloriuretic actions with the increase of endogenous creatinine clearance. CNP also elicited significant hypotensive actions (delta BPs/delta BPd: -4.3 +/- 1.3/-4.1 +/- 1.0 mm Hg) with the concomitant increase of heart rate (+7.6 +/- 2.6 bpm). Plasma aldosterone concentration significantly decreased from 45.4 +/- 2.3 to 35.4 +/- 4.9 pg/ml 30 minutes after the administration. Taken together, these results suggest a role for CNP in human renal function.

Vitamin D receptors repress basal transcription and exert dominant negative activity on triiodothyronine-mediated transcriptional activity

We have examined vitamin D receptor (VDR), thyroid hormone receptor (TR), and retinoid X receptor beta (RXR beta) binding to vitamin D response elements (VDREs), two thyroid hormone response elements (TREs) (DR4 and F2), and a retinoic acid response element (DR5). VDR/RXR bound well to the VDREs and to DR4 and DR5 using the electrophoretic mobility shift assay. Surprisingly, VDR/RXR also bound well to F2, which contains half-sites arranged as an inverted palindrome. In co-transfection experiments using CV-1 cells, we observed that VDR repressed basal transcription in the absence of ligand on DR3 and osteopontin VDREs and F2, but had no effect on DR4 or DR5. VDR selectively mediated ligand-dependent transcription on only VDREs. VDR also exhibited dominant negative activity as it blocked triiodothyronine (T3)-mediated transcriptional activity on DR4 and F2. These results demonstrate that VDR/RXR heterodimers can bind promiscuously to a wide range of hormone response elements, including inverted palindromes. Moreover, they show that unliganded VDRs, similar to TRs and retinoic acid receptors, can repress basal transcription. Last, they also suggest a novel repressor function of VDR on T3-mediated transcription which may be significant in tissues where VDR and TR are co-expressed.

The inhibitory effects of growth hormone-releasing hormone (GHRH)-antagonist on GHRH, L-dopa, and clonidine-induced GH secretion in normal subjects

The relative inhibitory potency of GHRH-Antagonist (GHRH-Ant) to GHRH(1-44)NH2 and mechanism of L-dopa- or clonidine-induced GH release were studied in seven normal subjects using GHRH-Ant. One hundred micrograms of GHRH-Ant (iv for 75 min) did not inhibit plasma GH responses to bolus injection of 100 micrograms and 10 micrograms GHRH or simultaneous infusion of 5 micrograms GHRH (iv for 75 min). However, 200 micrograms GHRH-Ant (iv for 75 min) significantly inhibited GH release, which was induced by simultaneous infusion of 5 micrograms GHRH. Although 100 micrograms GHRH-Ant could not significantly inhibit L-dopa-induced GH release, 200 micrograms GHRH-Ant almost completely inhibited the response. Similarly, the same dose of GHRH-Ant markedly inhibited the GH-releasing activity of clonidine. It is concluded that the inhibitory potency of GHRH-Ant on GHRH(1-44)NH2 is relatively weak (about 1/60 in molar base), and that L-dopa- or clonidine-induced GH release seems to be mediated by the release of hypothalamic GHRH.

[A case of selective IgM deficiency associated with systemic lupus erythematosus]

We report a case of selective IgM deficiency associated with systemic lupus erythematosus (SLE). A 34-year-old female suffering from SLE was admitted with proteinuria and general fatigue. Laboratory findings revealed a very low serum IgM level, almost lower than 12 mg/dl. Renal biopsy findings showed diffuse proliferative lupus nephritis (DPLN). In immunofluorescent microscopy, IgG was the most strongly stained followed by IgA, but IgM staining was only faint. As for the immunophenotype of the T cells, the OKT4/OKT8 ratio was normal. Response to both phytohemagglutinin (PHA) and concanavalin A (ConA) was normal. However, responses of B cells to both pokeweed mitogen (PWM) and Staphylococcus aureus Cowan strain I (SAC) were significantly reduced. Surface IgM-positive B cells were decreased. These results indicate that the patient had B cell dysfunction, involving impairment of B cell differentiation. In this report, we discuss selective IgM deficiency and SLE documented in the literature.

Plasma GH responses to human GHRH-antagonist in normal subjects

The effect of GHRH-antagonist [(N-Ac-Tyr1, D-Arg2) GRF-(1-29)-NH2] on plasma GH morning and evening secretion was evaluated in 14 normal subjects (10 males, 4 females, aged 19-25 years). Plasma GH was determined using a high sensitivity IRMA kit (detection limit, 0.006 micrograms/l). After intravenous infusion of GHRH-antagonist (100 micrograms/100 ml saline over 75 min) in the morning, plasma GH remained constant during the 150 min post-infusion (N = 6). In contrast, when GHRH-antagonist was administered in the evening, plasma GH showed a clear and gradual decrease through the initial 90 min and returned to baseline levels at 150 min. Plasma GH values were also significantly lower from 75 min to 135 min when compared to physiological fluctuations in plasma GH (P < 0.05). Other anterior pituitary hormones remained unaffected by GHRH-antagonist. In conclusion, our data suggest that evening basal GH secretion, but not morning GH secretion, is maintained by endogenous GHRH.

Altered gene expression of natriuretic peptide receptor subtypes in the kidney of stroke-prone spontaneously hypertensive rats

1. To elucidate the physiological and pathophysiological role of the natriuretic peptide system in the progression of hypertensive renal disease, we examined the gene expression of natriuretic peptide receptor subtypes, guanylate cyclase-A (GC-A), guanylate cyclase-B (GC-B) and clearance receptor (C receptor), in the kidney of stroke-prone spontaneously hypertensive rats (SHRSP) at 8 and 20 weeks of age, and compared them with their gene expression in age-matched Wistar-Kyoto (WKY) rats. 2. Northern blot analyses revealed that messages for three natriuretic peptide receptor subtypes were expressed in the kidney, and their expressions were higher in the glomeruli than in the whole kidney in each strain. 3. In 20 week old rats with established hypertension, the glomerular concentration of GC-A mRNA was significantly higher in SHRSP than in WKY. The concentrations of GC-B and C receptor mRNA in the glomeruli tended to increase and decrease, respectively, but they were not statistically significant in SHRSP. 4. In 8 week old rats, the glomerular concentrations of GC-A, GC-B and C receptor mRNA were not significantly different between SHRSP and WKY. 5. This study demonstrates that in the progression of hypertension, the expression of GC-A, which mediates biological actions of natriuretic peptides, is enhanced in the kidney of SHRSP compared to that of WKY. Together with the augmented secretion of the ligands previously revealed, altered expression of natriuretic peptide receptor subtypes in SHRSP may have a deterrent role in the development of hypertension and its renal complications.