Secretion of intrinsic factor from cultured rat gastric chief cells

Intrinsic factor (IF) is a vitamin B12 binding protein that is secreted from the gastric mucosa. We tested secretagogues which stimulate IF secretion in rat gastric perfusion and found that carbachol and cholecystokinin octapeptide (CCK-8) stimulated secretion, but histamine and tetragastrin did not. To confirm these results, we examined IF secretion from isolated rat chief cells. For this purpose, we established an enzyme immunoassay (EIA) using an avidin-biotin peroxidase complex to measure small amounts of IF. To prepare an anti-rat IF, IF was isolated from the stomach, and was injected into a rabbit for immunization. Rat gastric chief cells were isolated from the gastric mucosa with Dispase and a Percoll gradient centrifugation, and were cultured. We examined the effects of chemicals by adding them to culture dishes of chief cells in a CO2 incubator. Released IF in culture medium was determined by EIA. Carbachol, CCK-8 and secretin stimulated IF secretion from cultured chief cells, while histamine and tetragastrin did not; Forskolin and A23187 also stimulated the secretion. We concluded that carbachol and CCK-8 stimulated IF secretion via an increase of intracellular Ca2+ concentration and that secretin did so via a cAMP accumulation.

Inhibitory action of somatostatin on cAMP dependent pepsinogen secretion from rat gastric chief cells: involvement of pertussis toxin-sensitive G-protein

We examined the inhibitory effect of somatostatin on pepsinogen secretion using isolated rat gastric chief cells. Secretin and forskolin significantly increased not only pepsinogen secretion from chief cells but also cellular cAMP accumulation in a dose-dependent fashion. Somatostatin significantly inhibited secretin- and forskolin-induced pepsinogen secretion and secretin-induced cellular cAMP accumulation. However, forskolin-induced cellular cAMP accumulation was not inhibited by somatostatin. The inhibitory effect of somatostatin on secretin-induced pepsinogen secretion was abolished by pretreatment with pertussis toxin, but inhibition of forskolin-, carbachol- and cholecystokinin octapeptide-induced pepsinogen secretion was not. These results suggest that somatostatin inhibits pepsinogen secretion in two ways, one is closely related to the pertussis toxin-sensitive G-protein and the other is not determined.

[Evaluation of serum enzyme levels considering biological half lives of enzymes--alteration of lactate dehydrogenase isoenzyme pattern due to computer simulation]

The rapid clearance of certain releasing enzymes from blood stream may modify their usefulness as markers of disease. Serum LD isoenzyme patterns are often quite different from those in the affected tissues. Such differences result from differences in the biological half lives of the individual isoenzyme. In order to reveal such phenomena, we applied the one-compartment model to simulate the time dependent changes in the serum LD isoenzyme patterns as a most simple model. When we simulated leukemic cells as an affected origin, LD isoenzyme patterns obtained at a stage of clinical deterioration or active stage, were characterized by a high proportion of LD-2, LD-3 and LD-4, and resembled those of the original leukemic cells. In general, strong similarities in alterations of LD isoenzyme patterns were obtained between the clinical observed time course and simulated time course. These changes in LD isoenzyme patterns are practically observed in the cases of leukemia, lymphoma, and so on. If the original organs are identical, then it is change of disease stage that is responsible for modification of variable LD isoenzyme patterns. Such phenomena must therefore be noted--in doing so, we shall be able to estimate the origin of enzyme release, disease stage, and prognosis.

Differential effects of proteinase inhibitor camostat on exocrine pancreas in fed and fasted rats

Effects of an oral dose of the synthetic trypsin inhibitor camostat on pancreatic exocrine function were examined in rats that were either fasted from 12 h before feeding camostat to the end of experiments or fed ad libitum. Camostat (100 mg/kg body wt) caused significant increases in plasma cholecystokinin bioactivity (peak 13.4 +/- 2.0 pM at 30 min for fasted rats vs. 16.6 +/- 1.7 pM at 2 h for fed rats; not significant) and pancreatic exocrine secretion. In fed rats, but not in fasted rats, significant increases in pancreatic exocrine secretion were observed again at 12 h after a single oral dose of camostat (juice flow 10.3 +/- 0.4 microliters/20 min in fasted rats vs. 175.5 +/- 17.8 microliters/20 min in fed rats; P < 0.001), although pancreatic juice flow in fed and fasted control rats was nearly the same. When the pancreata from camostat-pretreated rats were isolated and perfused, the early effects of camostat on pancreatic exocrine secretion were abolished, whereas the late effects (12 h postfeeding) in fed rats were still observed (juice flow 33.7 +/- 3.4 microliters/20 min vs. control 2.8 +/- 0.4 microliters/20 min; P < 0.001). Thus, in addition to humoral and neural factors, persistent functional changes might have occurred in the pancreas of the fed camostat-pretreated rats. These present results indicate that oral camostat induces two different effects, immediate and delayed, on pancreatic exocrine secretory function. Camostat exerts its immediate effects in both fed and fasted rats, whereas delayed effects were induced only in fed rats.

[Evaluation of the postoperative regrowth of the acoustic neurinomas]

Although recent advances in microsurgical removal of acoustic neurinomas has made it possible to preserve, morphologically, the cochlear nerve as well as the facial nerve, functional impairment of the facial nerve is often encountered following total removal of the tumor. In order to avoid such functional morbidity, a surgical procedure can be proposed in which the tumoral capsule attached to a functional structure such as the facial nerve is intentionally left. Along with this surgical procedure and postoperative course observation, postoperative regrowth of the tumor should be precisely evaluated. A few recent reports about this problem have been published since CT scan and MRI have become available. The authors reviewed 66 cases in which postoperative evaluation by high resolution CT scan of the acoustic neurinomas has been carried out in their department more than one year after surgery. Multiple factors such as age at onset, sex, preoperative period, tumor size, vascularity, extent of the tumor removal, residual site, and pathological findings on HE stain were studied in relation to the tumor regrowth. Four cases showed regrowth of the tumor, and one of these tumors was reoperated on. The percentage of regrowth was 7.5% among the tumors which were not totally removed. No significant risk factors for tumor regrowth were noticed in these cases, but tumor regrowth tended to be found in younger patients. The residual tumors which showed regrowth were always located in the internal auditory meatus. In this study, it is apparent that, percentagewise, tumor regrowth is not so prevalent.(ABSTRACT TRUNCATED AT 250 WORDS)

[A meningioma in the posterior fossa without dural attachment: case report]

An extremely rare case of a meningioma in the posterior fossa without dural attachment has been reported. The patient was a 56-year-old male whose chief manifestation was the abnormality of his CT scan. His past history included gastric and colonic polyp when he was 54, 55 years old, and non-Hodgkin's lymphoma before hospitalization in our department. CT scan showed a small round non-enhancing lesion located at the lateral site of the right cerebellar cortex. T1 weighted image of MRI showed a homogeneous low intensity lesion with partial enhancing with Gd-DTPA. Proton image showed a remarkable low intensity lesion which showed an extramedullary mass. Right retromastoid craniectomy was performed. The mass was an extramedullary tumor which had no relation with the cerebellar cortex and dura matter. The arachnoid membrane around the tumor was intact. The tumor was totally resected and the patient had no neurological deficits. Histopathologically, the tumor was delineated into laminar structures by collagen fiber. Tumor cells were spindle in shape and made a whorling formation. There was no psammoma body and it had a hyperchromatic nuclei without mitotic features. Electron microscopic studies revealed no typical interdigitation but irregularity of the cell membrane. Abundant collagen fibers were in contact with basement membrane of the tumor. According to these findings, we diagnosed fibroblastic meningioma with atypical forms. Meningiomas without dural attachment are rare in adults, especially extremely rare of the posterior fossa. There are only 23 previous reports of "meningioma of the posterior fossa without dural attachment". Cantore divided these meningiomas into three groups (IV ventricle, inferior tela choroidea and cisterna magna).(ABSTRACT TRUNCATED AT 250 WORDS)

Somatostatin inhibits pepsinogen secretion without influencing cytosolic free Ca2+ increase induced by carbachol and cholecystokinin octapeptide in rat chief cells

Gastric chief cells were isolated from the rat stomach in an attempt to identify those involved in the mechanism of action of somatostatin on pepsinogen secretion. The effects of several kinds of secretagogues on cytosolic free Ca2+ concentration ([Ca2+]i) were examined in the rat chief cells. Carbachol and cholecystokinin octapeptide (CCK-8) markedly induced [Ca2+]i increase, while histamine, gastrin I and secretin did not. Carbachol and CCK-8 also stimulated pepsinogen secretion. A similar dose-response relationship was seen in carbachol- and CCK-8-induced [Ca2+]i increase and pepsinogen secretion. Somatostatin did not inhibit carbachol- or CCK-8-induced [Ca2+]i increase, but did inhibit carbachol- and CCK-8-induced pepsinogen secretion by 30 and 50%, respectively.

[Analysis of water content in young rats brain edema by Raman spectroscopy]

Cerebral edema, classified into vasogenic edema and cytotoxic edema, has long been studied and recognized to be complicated. The authors studied the cerebral edema models of young rats suffered from cryo-injury and triethyl tin chloride (TET) injury by Raman spectroscopy which can physiologically evaluate the cerebral water content (%) of very restricted area. The cryo-injury model was conducted in the following manner. A cryo-probe (-196 degrees C) was contacted to the exposed cranium for 20 seconds in an anesthetized 4-5-week-old Sprague-Dawley young rat. A coronal section of the injured brain covered with a slide glass and wrapped by Parafilm was obtained 2, 4, 6, 8, 12, 24, 48, 72 hours after the cryo-injury in order to measure the water content by Raman spectroscopy employed by Tashibu and Huizinga. TET injury model was obtained by intraperitoneal administration of TET (4.5 mg/Kg). The water content was observed by the same manner as for the cryo-injury model. Subsequent to the cryo-injury, the water content of the white matter which seemed to be higher than in adult rats increased rapidly and persisted in the same condition within 72 hours. Subsequent to TET injury, the water content of the white matter increased more rapidly than that of the gray matter, however, in adult rats the water content of the gray matter showed more rapid increase than that of the white matter. Increased water content followed by TET injury was higher in adult rats than in young rats.(ABSTRACT TRUNCATED AT 250 WORDS)

An ab initio molecular orbital study on effect of electric field strength on ionic selectivity of the sodium channel

The effect of electric field strength of the selectivity filter on ionic selectivity of the sodium channel has been studied by ab initio molecular orbital calculations. On the basis of the previous method, two kinds of model systems, the FCO2M system and the FCO2M-H2O system, were studied. In this study, a FCO2- molecule, which is substituted for a HCO2- molecule, was used as a model for the selectivity filter. This substitution corresponds to weakening the electric field strength of the selectivity filter. For this system, geometries of ground and transition states were optimized with MINI-3 basis sets. The FCO2-H2O system, for which we evaluated thermochemical parameters and cross-sections, is a good model for ionic permeation of the sodium channel. When the results of the FCO2M-H2O system were compared with those of the HCO2M-H2O system, we concluded that permeabilities of Li+ and Na+ are smaller and that of K+ is larger as the field strength of the selectivity filter is weakened. Namely, the permeation of K+ is relatively favorable when the field strength of the selectivity filter is weakened. This conclusion is in accordance with the prediction of Eisenman's theory.

A microneutralization enzyme immunoassay for antibody to human cytomegalovirus

We have developed a relatively rapid, sensitive and quantitative microneutralization assay for antibody to human cytomegalovirus (HCMV). Cell monolayers in 96-well microtiter plates inoculated with pre-incubated virus-antibody mixtures were fixed after 3 days. Infectious foci were stained with peroxidase-labeled human monoclonal antibody to a 64 kDa immediate early antigen of HCMV, and the plates were read at OD450. The 50% neutralization titer of the antibody was calculated. A study with 20 human sera and a human monoclonal antibody which neutralizes virus showed that this microneutralization enzyme immunoassay is more sensitive than, and as quantitative as, the conventional plaque reduction assay for antibody to HCMV. The neutralizing antibody titers of each sample measured by these two methods showed good correlation (n = 19, r = 0.884). Thus, this new assay is a useful and valid alternative to the conventional method for mass screening of sera and hybridoma fluids, and considerably more rapid.

[Plasma cholecystokinin levels in rats with pancreatic insufficiency induced by intra ductal injection of oleic acid]

Plasma cholecystokinin (CCK) levels in rats with pancreatic insufficiency induced by a single injection of 50 microliters oleic acid into the pancreatic duct were determined by a sensitive and specific bioassay using the isolated rat pancreatic acini. Treatment with oleic acid significantly decreased pancreatic wet weight within 7 days, which lasted until the end of observation (56 days). Histologic examination revealed the destruction of acinar cells and the epithelium of intra- and interlobular ducts. Plasma CCK bioactivity was significantly increased from the pre-treatment values of 0.8 +/- 0.1pM to 5.1 +/- 1.4pM at 24h after oleic acid treatment. After this peak, plasma CCK levels gradually decreased. Even after 56 days, however, plasma CCK levels in oleic acid-treated rats were significantly high compared with those in control rats. In the present study, plasma CCK levels in rats with chronic pancreatitis did not correlate with the progress of pancreatic insufficiency.

Involvement of endogenous cholecystokinin in the development of acute pancreatitis induced by closed duodenal loop

Involvement of endogenous cholecystokinin (CCK) in the development of acute pancreatitis induced in rats by closed duodenal loop (CDL) was examined, and the effects of the potent and specific CCK receptor antagonist loxiglumide on this model of acute pancreatitis were evaluated. Plasma CCK bioactivity was markedly elevated 3 and 6 h after onset of acute pancreatitis. A single subcutaneous injection of 50 mg/kg body wt of loxiglumide 30 min before the induction of acute pancreatitis completely eliminated the hypercholecystokinemia. Loxiglumide given 3 h after the induction of acute pancreatitis suppressed plasma CCK bioactivity, which had risen up to 30-fold over basal value (0 h) at 3 h, to nearly the basal level. Loxiglumide pretreatment, in addition, significantly prevented the rise in serum amylase and lipase activity, as well as the increase in ascitic volume. It also ameliorated histological alterations of hemorrhagic and necrotizing pancreatitis. Reduction of plasma CCK bioactivity by loxiglumide after the onset of pancreatitis slowed the rate of progression of pancreatitis. However, pancreatic wet weight and cellular infiltration were not significantly influenced by loxiglumide treatment. These observations suggest that endogenous CCK is not involved in the initiation of acute hemorrhagic and necrotizing pancreatitis induced by CDL, but is involved in the development of pancreatitis in this model.

[Inhibitory effect of somatostatin analog, SMS 201-995, on exocrine secretion from isolated rat pancreatic acini]

In vitro effect of somatostatin analog, SMS 201-995 (SMS), on pancreatic exocrine secretion was investigated using isolated rat pancreatic acini. SMS had no effect on basal, cholecystokinin octapeptide (CCK-8)- or secretin-stimulated amylase release. SMS inhibited pancreatic amylase release in response to simultaneous stimulation with secretin and CCK-8 in a dose-dependent manner. Significant inhibition was observed with 10 nM SMS and maximal inhibition with 0.1-1 microM SMS. Amylase release in response to the combination of 100 pM CCK-8, 1 nM secretin and 0.1-1 microM SMS was similar to that to 100 pM CCK-8 alone. Secretin significantly increased acinar cell cAMP content. SMS partially inhibited an increase in cAMP content induced by secretin. The present study has demonstrated, therefore, that SMS directly inhibits the potentiating effect of secretin on exocrine secretion in part by inhibiting an increase in secretin-induced cAMP accumulation in rat pancreatic acinar cells.

Primary cardiac hemangiopericytoma causing rupture of the right atrium and chronic cardiac tamponade

A 53-year-old woman presented with symptoms of dyspnea on exertion and edema of lower extremities. Chronic cardiac tamponade caused by the rupture of the right atrial wall was diagnosed by two-dimensional contrast echocardiography. Autopsy findings revealed primary cardiac hemangiopericytoma.

[Changes in lumbosacral canal length during flexion and extension--dynamic effect on the elongated spinal cord in the tethered spinal cord]

This clinical research has been conducted to extend the understanding of pathophysiological mechanism involved in the tethered cord syndrome. In normal individuals, the filum terminale has elasticity similar to the rubber band. This allows cephalad or caudad movement of the lumbosacrococcygeal spinal cord while the spine is flexed or extended. This is based on the observation that the lowest pair of dentate ligaments spans from the T12 and L1 junction of cord segments to the dura between the dural exit of T12 and L1 nerve roots, and the spinal cord below T12 can freely ascends on flexion and descends in the spinal canal on extension of the spine. In 50 healthy human subjects, x-ray films of the thoracolumbosacral spine were studied. Lateral films of the spine were taken in the neutral, hyperextended and hyperflexed positions. The first group included 10 individuals whose ages ranged from 27 to 42 years. The distance between the middle of the T10 vertebra and L1-L2 interspace was measured. This distance was considered to represent the length of the lumbosacral cord segment (L1 through coccygeal cord segments). The second group included 40 individuals whose ages ranged from 17 to 50 years. The distance between the L1-L2 interspace and S1-S2 interspace was measured. The distance signified the distance between the caudal end of the spinal cord and attachment of filum terminale to the sacrum. There was a 3.5% (4.6mm by X-ray films) increase during hyperflexion in the distance measured in the first study.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ethanol on pancreatic exocrine secretion in rats

The effect of ethanol on pancreatic exocrine secretion was studied in isolated rat pancreatic acini. Ethanol caused a dose-dependent stimulation of amylase release, and a twofold increase of amylase release was observed with 600 mM ethanol. Ethanol inhibited cholecystokinin octapeptide (CCK-8)- and carbamylcholine-stimulated amylase release and similarly inhibited binding of [125I]CCK-8 and [N-methyl-3H]scopolamine to isolated rat pancreatic acini in a dose-dependent manner. The inhibitory effect of ethanol was fully reversible with respect to CCK-8-induced amylase release. On the other hand, ethanol potentiated secretin- and vasoactive intestinal peptide (VIP)-stimulated amylase release. Ethanol induced a small but significant increase in Ca2+ efflux, whereas CCK-8 induced an immediate and large increase, but ethanol significantly inhibited CCK-8-stimulated Ca2+ efflux. The present study clearly demonstrates the dual effects of ethanol on pancreatic exocrine function: stimulation and inhibition. We suggest that mobilization of intracellular Ca2+ may be involved in the mechanism of ethanol's action on isolated rat pancreatic acini.

Preliminary X-ray crystallographic analysis of tryptophanase from Escherichia coli

Tryptophanase (L-tryptophan indole-lyase) from Escherichia coli has been crystallized from ammonium sulfate solution using a vapor diffusion method. The crystals are tetragonal and belong to space group P4(1)2(1)2 or its enantiomorph. The cell dimensions of the crystals are a = b = 113.4 A, and c = 232.2 A, with two subunits per asymmetric unit. The crystals diffract to at least 3 A resolution, and are suitable for X-ray structural analysis.

A case of cardiac amyloidosis presenting with symptoms of exertional syncope

A 54-year-old man presented with symptoms of exertional syncope. Cardiac amyloidosis was diagnosed by endomyocardial biopsy. Exercise tolerance test revealed a failure of increased heart rate followed by sinus arrest, associated with syncope. Autopsy revealed amyloid deposits in the sinoatrial node.

Enzymatic degradation of helodermin and vasoactive intestinal polypeptide

Helodermin (HDM) belongs to the vasoactive intestinal polypeptide (VIP) family of polypeptides. Degradation of HDM in the tracheal tissue isolated from a guinea-pig and by an isolated enkephalinase was studied and compared with the degradation of VIP. The tracheal relaxing activity of VIP was potentiated by enkephalinase inhibitors, thiorphan and phosphoramidon, while the activity of HDM was not potentiated. On the other hand, bestatin, an aminopeptidase inhibitor, and captopril, an angiotensin converting enzyme inhibitor, did not influence the activity of VIP and HDM. The data suggests that the degradation of VIP but not HDM in the trachea was done by enkephalinase. Enkephalinase was then purified from the lung and the striatum membrane fraction through a DEAE-cellulose column, chromatofocusing column and hydroxyapatite column. The purified enkephalinase from the lung hydrolyzed VIP but not HDM. HDM and VIP were, however, hydrolyzed by the striatum enkephalinase. There was only a partial degradation of HDM by the striatum enkephalinase and the hydrolysis rate of HDM was slower than that of VIP. The degradation of VIP and HDM was inhibited by thiorphan. In conclusion, we found that VIP but not HDM was degraded by enkephalinase present in the respiratory system such as the trachea and the lung. Furthermore, enkephalinase, which hydrolyses HDM, was present in the brain.

[A case of pseudo-TSH.PRL-producing pituitary adenoma with secondary hypothyroidism]

A 24-year-old housewife presented with weight gain of about 30 kg, constipation and pitting edema of extremity nine years after having a thyroidectomy. Hormonal examination revealed low levels of serum T3 and T4 and high levels of serum TSH and PRL. She also had enlarged pituitary gland (pituitary hyperplasia) with suprasellar extension on CT and MRI image. Thyroid replacement therapy and follow-up by MRI were performed without resort to surgery, because she had no visual disturbance. Within about 1 month after thyroid replacement therapy, serum TSH and PRL were normalized. And also thyroid function was normalized by thyronine (T3). Following this results, pituitary hyperplasia regression was seen on MRI image. About 1 year after thyroid replacement therapy, pituitary hyperplasia regression was more seen on MRI image. Prolonged hypothyroidism can result in hypertrophy of the pituitary thyrotropin-secreting cells and prolactin secreting cells. So, it can increase pituitary weight (pituitary hyperplasia). Radiological examination, abnormal sellar x-ray films suggesting intrasellar tumor are common in patients with primary hypothyroidism. Suprasellar extension of pituitary mass (pituitary hyperplasia) due to hypothyroidism was reported by radiological examination (PEG, CT and MRI image), and regression of pituitary hyperplasia was revealed by radiological examination after thyroid replacement therapy. The first choice of this type of pituitary hyperplasia is thyroid replacement therapy unless the patient has a visual disturbance. However, if this replacement therapy is not effective for diminution of the tumor, surgical removal of the tumor should be considered.

Apodemus sylvaticus, a new host for Acanthocheilonema viteae (Nematoda: filarioidea)

Susceptibility of Apodemus sylvaticus and A. agrarius to infection with Acanthocheilonema viteae was compared with that of hamsters and jirds. Microfilaremia in A. sylvaticus was first noted on day 52 post-infection (p.i.) and lasted during the course of the study (up to day 150 p.i.). Maximum microfilaremic levels (female worm basis) of A. sylvaticus [mean +/- S.D. (n) = 690 +/- 1288(6)] were considerably higher than those of hamsters [16 +/- 18(6)] and jirds [51 +/- 25(5)]. Adult worm recovery in A. sylvaticus ranged from 2 to 40% of the number of infective larvae inoculated. Worm development in A. sylvaticus resembled that in hamsters and jirds. In contrast, microfilaremia was not detected in, nor adult worms recovered from A. agrarius throughout the study.

[A case of solitary syringobulbia]

A case of solitary syringobulbia without syringomyelia diagnosed by MRI was reported. A 63-year-old female, who had a history of progressive gait disturbance for 9 months, was admitted to our department because of severe headache. Neurological examination revealed that the patient was suffering from right pyramidal sign as well as left deep sensory disturbance without apparent impairment of cranial nerves or nystagmus. The somatosensory evoked potential stimulated by the left median nerve showed delay in latency and low amplitude, however, the auditory brainstem response showed normal records bilaterally. A syringobulbia associated with platybasia, basilar impression, obstructive hydrocephalus and Arnold-Chiari malformation was diagnosed by the neuroradiological examinations including plain X-ray films of the skull, CT scan and MRI of the brain. Subsequent to the decompression around the cisterna magna by suboccipital craniectomy and laminectomy of the atlas, the opening of the Foramen Monro which was obstructed by a thick membrane was carried out, and prevention of communication between the fourth ventricle and the syrinx was accomplished by using a piece of muscle. This operative procedure was thought to be compatible with Gardner's operation for syringomyelia. The patient showed gradual improvement of gait disturbance as well as headache 3 months after surgery, and this neurological improvement was proved by decrease in the size of the known syringobulbia on MRI, and by normalized somatosensory evoked potential stimulated by the median nerve. Pathophysiology of the solitary syringobulbia with relatively acute onset of the neurological symptoms was assumed to have taken place in the following manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of tryptophan 248 in the active site of tryptophanase from Escherichia coli

Tryptophan 248, located in the active site of tryptophanase from Escherichia coli, has been replaced with phenylalanine by site-directed mutagenesis. Judging from CD and fluorescence spectra, the global structure of the mutant enzyme was found to be the same as that of the wild-type enzyme. The binding affinity of the mutant enzyme for the coenzyme pyridoxal 5'-phosphate (PLP) was reduced tenfold compared to the wild-type enzyme. Kinetic analyses under PLP-saturated conditions indicated that the Km values of the mutant enzyme for substrates are the same as those of wild-type enzyme but the kcat values are decreased to about 85%, which accounts for the overall activity decrease. These findings suggest that tryptophan 248 interacts closely with PLP and plays an important role in the catalytic reaction.

Plasma atrial natriuretic peptide in young normotensive subjects with a family history of hypertension and in young hypertensive patients

Plasma atrial natriuretic peptide (ANP) behavior was evaluated in 26 untreated essential hypertensives, 21 normotensives, and 20 normotensives with hypertensive heredity under normal sodium intake (120 mEq of Na+/day). All subjects were men, mean age 22.1 +/- 1.9 years. Plasma ANP was evaluated by radioimmunoassay on samples collected in supine position upon waking and again after 1 h of orthostatism. Resulting data showed that ANP in hypertensives (supine = 44.5 +/- 19.4 pg/mL, orthostatism = 24.1 +/- 11.6 pg/mL) was at higher levels than in controls (supine = 38.3 +/- 19.4 pg/mL, orthostatism = 19.9 +/- 10.6 pg/mL) or in normotensives with hypertensive heredity (supine = 42.1 +/- 16.8 pg/mL, orthostatism = 23.2 +/- 10.8 pg/mL). Mean ANP level was higher in the latter group than in the control group (supine = +9%; orthostatism = +14.2%). In conclusion, plasma ANP is raised in young essential hypertensives, resulting in slightly elevated levels in normotensives with hypertensive heredity.