Rostral medullary cholinergic mechanisms and chronic stress-induced hypertension

This work was designed to study the relationship between the cholinergic mechanisms in the rostral ventrolateral medulla (rVLM) and the incidence of hypertension induced by chronic stress. Under anaesthetized conditions, bilateral microinjection of scopolamine (1.18 nmol/site) into the rVLM produced a much greater depressor response in chronic stress-induced hypertensive rats than in normotensive rats. Similar bradycardic effects were observed in both the normotensive and the hypertensive rats when scopolamine was injected into the rVLM. Acetylcholine (Ach) content and choline acetyltransferase (ChAT) activity in rostral medulla were determined by radioimmunoassay both in the normotensive and the hypertensive rats. Ach content and ChAT activity increased significantly in the hypertensive rats, and such increase mainly occurred within the ventral part of the rostral medulla. These results suggest that the cholinergic mechanisms in the rVLM may be activated during chronic stress and such activation may be involved in the pathogenesis of the hypertension induced by chronic stress.

Hormonal mechanism of sodium oleate-stimulated pancreatic secretion in rats

We have investigated the role of two intestinal hormones, secretin and cholecystokinin (CCK), on the pancreatic exocrine secretion stimulated by sodium oleate in anesthetized rats. Each rat was prepared with a polyethylene tube in the proximal duodenum and ligation of the pylorus. To collect pancreatic juice, the common bile-pancreatic duct was cannulated near the duodenal wall while bile was diverted to the exterior. Intraduodenal infusion of sodium oleate at doses of 0.03, 0.06, 0.12, and 0.24 mmol/h resulted in significant increases in pancreatic secretion including fluid, bicarbonate, and protein output. The increases of the three parameters were dose dependent and were correlated well with the increases in plasma secretin and CCK concentrations. To further clarify their hormonal roles, we have repeated identical experiments under intravenous administration of a rabbit anti-secretin serum (0.1 ml) or CR 1409 (4 mg.kg-1.h-1), a CCK-receptor antagonist, or a combination of both the antiserum and CR 1409. The antiserum significantly suppressed volume flow and bicarbonate secretion with a minor inhibitory effect on protein secretion, whereas a normal rabbit serum did not. CR 1409 significantly suppressed all three parameters. The combined treatment with both the antiserum and CR 1409 almost completely abolished the pancreatic secretion. Atropine given intravenously significantly inhibited the protein output but did not influence volume flow or bicarbonate output in response to sodium oleate. We thus conclude that, in rats, fat-stimulated pancreatic secretion of volume flow and bicarbonate depends entirely on the circulating endogenous secretin and CCK but that the protein output appears to be under control of both hormonal and cholinergic controls.

Mechanism of acid-induced release of secretin in rats. Presence of a secretin-releasing peptide

In fasting rats, intraduodenal infusion of dilute hydrochloric acid results in significant increases in both pancreatic exocrine secretion and plasma concentration of secretin. To test the hypothesis that acid-induced release of secretin is mediated by a secretin-releasing factor (S-RF), anesthetized rats were prepared with pyloric ligation, duodenal and jejunal cannulas, and pancreatic duct cannulas. Donor rats were infused intraduodenally with 0.01 N HCl, 0.15 M NaCl, or a combination of 0.01 N HCl and 0.05 N NaHCO3 at 0.3 ml/min for 1.5 h, and the perfusates were collected via jejunal cannulas. The perfusates with pH adjusted to 6.0 were concentrated threefold and infused into the duodena of recipient rats. The concentrate of acid perfusate (CAP) significantly increased both pancreatic volume flow and bicarbonate output and plasma concentration of secretin, whereas concentrates of the saline perfusate (CSP) or the perfusate of a combination of 0.01 N HCl and 0.05 N NaHCO3 (CABP) did not influence pancreatic secretion or plasma concentration of secretin. The increased pancreatic secretion by CAP was attributed to increased circulating secretin because when secretin was immunoneutralized by a rabbit antisecretin serum, CAP-stimulated pancreatic secretion was abolished. The bioactivity of CAP was trypsin-sensitive and heat stable. The active substance in CAP had a molecular weight of less than 5,000 and greater than 1,000, as determined by ultrafiltration and bioassay. In conclusion, dilute HCl releases an S-RF into the upper small intestinal lumen to stimulate release of secretin. This substance, with molecular weight of less than 5,000, is heat stable and trypsin sensitive. Thus, the acid-stimulated release of secretin is mediated by a secretin-releasing peptide in the upper small intestinal lumen.

Spinal cord substance P mediates carbachol-induced cardiovascular responses from the rostral ventrolateral medulla

Intrathecal (i.t.) infusion of substance P (SP) antagonist, (D-Pro2, D-Trp7,9)-substance P (20 micrograms), lowered blood pressure profoundly without any significant change of heart rate. The hypertensive and tachycardic responses elicited by microinjection of carbachol (25 ng/site) into the bilateral rostral ventrolateral medulla (rVLM) were blocked by i.t. infusion of SP antagonist. These data provided evidence that an excitatory cardiovascular effect induced by cholinergic system in rVLM may be mediated mainly by the SP receptors in spinal cord.

Photothermal radiometry measurement of thermal diffusivity

A method of measuring the thermal diffusivity of solid material at room temperature with photothermal radiometry is described. By measuring the amplitude and phase frequency characteristics of the photothermal signal, the thermal diffusivity is calculated and compared with the value obtained by the pulsed laser conductometer method.

[Investigation on resources of the Chinese drug beimu in Gansu Province]

Based on a resources investigation and taxonomic research on the medicinal plants of Fritillaria from Gansu Province. Nine species one variety and one cultivation variety have been reported. Records and distribution of the species, together with a key for the species and a key for the powdered drug have been furnished as well.

Effect of pancreatic proteases on plasma cholecystokinin, secretin, and pancreatic exocrine secretion in response to sodium oleate

The effect of pancreatic proteases or juice on the sodium oleate-stimulated pancreatic secretion and plasma concentrations of secretin and cholecystokinin in anesthetized rats was investigated. Each rat received sodium oleate in a dose of 0.12 mmol.h-1 via a duodenal tube. Sodium oleate infusion significantly increased pancreatic secretion (volume and protein output) compared with the saline given the control group. The increase in pancreatic secretion paralleled significant elevations of plasma concentrations of secretin and cholecystokinin. To determine a possible role of pancreatic proteases on the responses induced by sodium oleate, saline, chymotrypsin, and trypsin, a combination of chymotrypsin and trypsin or pancreatic juice was infused into the duodenum. The pancreatic secretion was significantly reduced by pancreatic proteases or pancreatic juice, and the reduction paralleled the decreases in plasma concentrations of the two hormones. These agents suppressed both pancreatic secretion and plasma hormone levels in the following order of magnitude: (pancreatic juice or chymotrypsin + trypsin) greater than (trypsin) greater than (chymotrypsin). The reduction of pancreatic secretion by pancreatic proteases was reversed by intravenous administration of secretin and cholecystokinin in physiological doses. It is concluded that negative-feedback regulation of pancreatic secretion is operative in the intestinal phase in rats and that both secretin and cholecystokinin are involved in the regulation.

Microvascular decompression by retrosigmoid approach for trigeminal neuralgia: experience in 200 patients

Trigeminal neuralgia is often seen in elderly persons. Two hundred patients with trigeminal neuralgia were submitted to microvascular decompression by a retrosigmoid approach. The surgical procedure is described. Vascular compression of the nerves was noticed in all these patients at operation. One hundred ninety-seven had relief of symptoms postoperatively, for a 98.5% cure rate. In addition, we suggest that another important cause is arteriosclerosis.

Enhanced slow-pressor response to angiotensin II in spontaneously hypertensive rats

Rapid-pressor and slow-pressor responses to angiotensin (ANG) II and norepinephrine (NE) in spontaneously hypertensive rats (SHR) and Wistar Kyoto control rats (WKY) were examined. All animals were treated from 4 wk of age with captopril (100 mg/kg/day in drinking water) to prevent development of hypertension so that changes in responsiveness could not be attributed to disparate base-line blood pressures or to hypertension-induced injury of the cardiovascular system. In 11-wk, conscious, unrestrained, captopril-treated rats, ANG II and NE induced rapid-pressor responses (i.e., a rapid increase in arterial blood pressure that reached a maximum within 10 min) that were of similar magnitude in SHR and WKY. In an additional group of 9-wk captopril-treated rats, both ANG II and NE caused slow-pressor responses (i.e., a slow increase in arterial blood pressure over 2 wk). Although the slow-pressor response to NE was similar in SHR versus WKY, the slow-pressor response to ANG II was much greater in SHR compared with WKY. Further studies were conducted in captopril-treated (from 4 wk of age) SHR and WKY to investigate whether the increased slow-pressor response to ANG II in SHR was mediated by an enhanced ability of ANG II to potentiate peripheral sympathetic neurotransmission, contract vascular smooth muscle, increase sympathetic tone to nonadrenal sites, release aldosterone, and/or reduce renal function. No evidence was found that supported a role for the aforementioned nonrenal actions of ANG II. However, 11-wk captopril-treated SHR were 10-fold more sensitive to the antidiuretic, antinatriuretic, and renal vascular effects of intrarenal infusions of ANG II compared with captopril-treated WKY. Also, chronic (1 wk) intrarenal infusions of a very low dose of ANG II (1 ng/min) caused a marked slow-pressor response in 11-wk captopril-treated SHR but did not alter arterial blood pressure in WKY. We conclude that 1) the slow-pressor response to ANG II is greatly enhanced in SHR, 2) this enhancement is specific with respect to type of response (slow not rapid) and pressor agent (ANG II not NE), 3) a genetic defect underlies the increased slow-pressor response to ANG II in SHR, and 4) the enhanced slow-pressor response to ANG II contributes significantly to the pathophysiology of hypertension in SHR. Finally, the current studies are consistent with our working hypothesis that the kidneys mediate the enhanced slow-pressor response to ANG II in SHR.

The expression frequency of common fragile sites and genetic susceptibility to lung cancers

The chromosomal aberration rate (including gap and break) and expression frequency of common fragile sites were examined in peripheral blood lymphocytes cultured with TC199 medium from 96 patients with lung cancers, 40 of their first-degree relatives, and 45 normal control subjects. Both the chromosomal aberration rates and expression frequencies of common fragile sites observed in patients and their relatives were significantly higher than those in normal control subjects. About 60% of chromosomal aberrations were derived from the expression of common fragile sites either in the patients and their relatives or in the controls. The expression of fra(3)(p14) was most frequently observed, and the mean frequencies of its expression in patients and their relatives were significantly higher than in control subjects. It is suggested that common fragile sites might be unstable factors of the human genome, and their expression might be affected by some genetic factors, and they might play an important role in the genetic susceptibility to lung cancers. The significantly high expression of fra(3)(p14) in patients and their relatives may be related to the generation of the breakpoint at band 3p14 found in lung cancers.

Genetic studies on the inability of beta-galactosidase to be translocated across the Escherichia coli cytoplasmic membrane

When a signal sequence is attached to beta-galactosidase, the normally cytoplasmic protein is unable to fully traverse the cytoplasmic membrane. We used a genetic approach to study those features of beta-galactosidase responsible for the block in translocation. By using both in vivo and in vitro techniques, fragments of beta-galactosidase were interposed between a signal sequence and alkaline phosphatase. The alkaline phosphatase acts as a sensor for any blocking effects of beta-galactosidase on export. From these studies, we show that multiple regions of beta-galactosidase contribute to its failure to be translocated. These results are most easily interpreted if the folding of beta-galactosidase or of domains of it is responsible for the block in export. In addition, in certain constructs, positively charged amino acids directly following the signal sequence interfered with export.

Adenosine-angiotensin II interactions. Part II. The role of adenosine in regulating angiotensin II-induced changes in heart rate and aldosterone release

The purpose of the present study was to determine whether endogenous adenosine (ADO) participates in angiotensin II (AII)-induced decreases in heart rate (HR) and regulates AII-induced aldosterone (ALDO) release. To test these hypotheses we investigated: 1) the effects of ADO and AII on base-line HR and ALDO levels; 2) the effects of ADO on AII-induced bradycardia and AII-induced increases in ALDO levels; 3) the effects of ADO receptor antagonists [caffeine and/or 1,3-dipropyl-8-p-sulfophenylxanthine (DPSPX)] on AII-induced bradycardia and AII-induced increases in ALDO levels; and 4) the effects of ADO receptor hypersensitivity on AII-induced bradycardia. In the latter experiments, the animals were rendered hypersensitive to the bradycardic effects of ADO by administering caffeine for 1 week then abruptly withdrawing caffeine 18 hr before the experiment, i.e., caffeine withdrawal. Intravenous infusions of either ADO or AII decreased base-line HR and ADO reduced the bradycardic response to AII. Intravenous infusions of DPSPX attenuated and caffeine withdrawal potentiated AII-induced bradycardia without modifying AII-induced increases in arterial blood pressure. AII increased and ADO did not alter base-line plasma ALDO levels; however, ADO attenuated by 50% AII-induced increases in ALDO levels. Neither DPSPX nor caffeine altered the ability of AII to increase plasma ALDO levels. These results indicate that although ADO has the potential to modulate AII-induced increases in plasma ALDO concentrations, endogenous ADO does not regulate the effects of AII on plasma ALDO levels under the conditions of these studies. However, endogenous ADO, in some way, contributes substantially to AII-induced bradycardia.

An improved method of direct chromosome preparation from chorionic villus and high resolution banding technique

The trophoblast was dissociated from the underlying mesenchymal layer either with acetic acid after short-term prefixation or with mechanical power after fixation twice. The colcemid treatment time was shorted to 16 min and trypsin solution of low pH (6.2) was used for banding. By these steps, the quality of chromosome banding was greatly improved and complete standard chromosome diagnoses were made in 24 of 24 cases. With the modified technique, high resolution banding chromosomes were consistently obtained after short-term incubation.

[Diagnosis of smooth muscle tumor of the small bowel]

In this report, the experience in the diagnosis of smooth muscle tumor of the small bowel in 32 cases (14 leiomyomas and 18 leiomyosarcomas) was presented. The authors discussed the clinical features, the pathological classification of the tumor, the diagnosis of intestino-intestinal fistula, and ways to improve its preoperative diagnosis.

The mature portion of Escherichia coli maltose-binding protein (MBP) determines the dependence of MBP on SecB for export

The product of the secB gene is required for export of a subset of secreted proteins to the outer membrane and periplasm of Escherichia coli. Precursor maltose-binding protein (MBP) accumulates in the cytoplasm of secB-carrying mutants, but export of alkaline phosphatase is only minimally affected by secB mutations. When export of MBP-alkaline phosphatase hybrid proteins was analyzed in wild-type and secB-carrying mutant strains, the first third of mature MBP was sufficient to render export of the hybrid proteins dependent on SecB. Substitution of a signal sequence from a SecB-independent protein had no effect on SecB-dependent export. These findings show that the first third of mature MBP is capable of conferring export incompetence on an otherwise competent protein.

[Role of rostral ventrolateral medulla in the pressor response to intracerebroventricular injection of neostigmine]

Experiments were carried out on 47 urethane-chloralose anesthetized and flaxedil immobilized rabbits under artificial respiration. Intracerebroventricular injection (ICV) of neostigmine (100 micrograms/200 microliters) caused a marked increase in blood pressure (BP), left ventricular pressure (LVP) and renal sympathetic nerve discharge (RND), while femoral blood flow (FBF) and conductance (COND), were decreased and the heart rate (HR) was initially reduced and then slightly increased. Microinjection of atropine (0.25 micrograms/site) into the rostral ventrolateral medulla (rVLM) caused a decrease in BP, HR, RND and LVP and a increase in FBF and COND. Pretreatment of atropine injection into rVLM before ICV of neostigmine blocked the pressor response of neostigmine. These results indicate that rVLM is important for the pressor response to ICV neostigmine, which may be mediated via cholinergic muscarinic receptors in rVLM.

Ticlopidine in China: comparative study on the effect of two dose levels on bleeding time and platelet function in healthy volunteers

The compared inhibitory effects of two dose levels of ticlopidine (250 and 500 mg/day) on bleeding time and platelet function in Chinese volunteers have been studied in a placebo-controlled study. Ticlopidine exerted several significant effects: namely prolongation of bleeding time, inhibition of ADP-induced platelet aggregation, reduction of the thromboxane B2 synthesis induced by collagen as well as by ADP. The daily dose of 250 mg did not show significantly different effects as compared to the western, usually recommended daily dose of 500 mg. At the daily dose of 500 mg, adverse reactions occurred more frequently than at the daily dose of 250 mg, but no serious side effects necessitating discontinuation of treatment, or abnormalities in hematological and liver function parameters were observed at these two dose levels. In Chinese people, ticlopidine therapy should be administered at a daily dose of 250 mg.

Inhibition of baroreflex following microinjection of GABA or morphine into the nucleus tractus solitarii in rabbits

The possibility that putative transmitters may influence the aortic nerve stimulation-produced bradycardia and depressor responses was examined in urethane- and chloralose-anesthetized, paralyzed and artificially ventilated rabbits. The ipsilateral microinjection of gamma-aminobutyric acid (GABA, 2-4 micrograms) or morphine hydrochloride (2-4 micrograms) into the nucleus tractus solitarii (NTS) area could partially block the evoked bradycardia and depressor responses produced by stimulation of the aortic nerve without influencing the basal blood pressure and heart rate. This blocking effect of either GABA or morphine was dose-related. Pretreatment with GABA receptor antagonist bicuculline methiodide (0.15-0.20 micrograms) and opiate receptor antagonist naloxone hydrochloride (1-2 micrograms) into the same medullary area completely abolished the effect of GABA and morphine, respectively. Application of bicuculline also greatly antagonized the effect of morphine, but the blocking effect of GABA on the evoked bradycardia and depressor responses still existed following the pretreatment of naloxone. These results indicate that GABAergic and opiate systems present at the NTS exert an inhibitory influence on the evoked baroreflexes and inhibitory effect of the latter may be related to the activation of GABAergic receptor in this nucleus.

Stimulation of the ventrolateral medulla inhibits the baroreceptor input to the nucleus tractus solitarius

Extracellular recording experiments were done in urethane- and chloralose-anaesthetized, paralyzed and artificially ventilated rabbits. Thirty-one baroreceptor-sensitive neurones were identified in the region of the nucleus tractus solitarius (NTS) by their excitatory responses to stimulation of the ipsilateral aortic nerve. A conditioning stimulus delivered to the ipsilateral or contralateral rostral ventrolateral medulla (rVLM) inhibited the excitatory responses of 80.0% (19 out of 24) neurones to an aortic test stimulus as early as 3 ms and extending as long as 400 ms after conditioning. The same inhibitory effect was also observed by application of excitant amino acid DL-homocysteic acid (0.2 M, 100 nl) into the ipsi- or contralateral rVLM area in 6 units. In 5 units inhibited by rVLM stimulation, evoked discharges were inhibited by prolonged electrical stimulation of the superficial peroneal nerve (SP) with low intensity and low frequency (0.1-0.3 mA and 5-10 Hz). These results provide the electrophysiological evidence for the suppressing effect of the rVLM on the excitatory responses of NTS neurones to baroreceptor afferent stimulation.

Identification of enterotoxigenic Escherichia coli isolates with enzyme-labeled synthetic oligonucleotide probes

Commercially available kits containing alkaline phosphatase-labeled oligonucleotide probes for Escherichia coli heat-stable enterotoxins (STI-H, STI-P, and STII) and the heat-labile enterotoxin were compared with bioassays and radiolabeled recombinant DNA probes to identify enterotoxigenic E. coli from 100 clinical isolates. There was very good agreement between the three methods.

Alteration of the amino terminus of the mature sequence of a periplasmic protein can severely affect protein export in Escherichia coli

Escherichia coli alkaline phosphatase, coded for by the phoA gene, is normally translocated across the cytoplasmic membrane into the periplasm with high efficiency. We have constructed a series of derivatives of the phoA gene that code for a wild-type signal sequence but result in altered amino acid sequences at the amino terminus of the mature alkaline phosphatase. Our results suggest that the presence of two positively charged amino acids very early in the mature sequence interferes significantly with protein export. In one case, phoA2AB, the presence of the sequence Arg-Ile-Arg at the amino terminus of alkaline phosphatase results in a 50-times reduction in the export of the protein. By using oligonucleotide-directed mutagenesis, we have constructed mutant derivatives of phoA2AB that are greatly enhanced for export. In all cases, these derivatives reduce the net positive charge in the region. Our results may explain the failure of E. coli to export a number of proteins coded for by artificial constructs and suggest a way to improve export in these cases.

A GABAergic mechanism in the inhibition of cardiac vagal reflexes

A depressor response and bradycardia were produced by aortic nerve stimulation in urethane-chloralose-anaesthetized, paralyzed and artificially ventilated rabbits. Stimulation of the superficial peroneal nerve (SP) or rostral ventrolateral medulla (rVLM) inhibited the aortic nerve stimulation-evoked bradycardia, which was also inhibited by direct microinjection of GABA into the dorsal vagus nucleus (DVN). Application of bicuculline methiodide into the same medullary area antagonized the effect of GABA and partially or completely abolished the SP or rVLM stimulation-produced inhibition. However, strychnine hydrochloride had no effect on the SP or rVLM stimulation-produced inhibition. These observations indicate that GABAergic system present at the DVN is possibly involved in the inhibition of evoked bradycardia during somatic afferent and rVLM stimulation.

Adenosine in renin-dependent renovascular hypertension

Our previous studies support the hypothesis that activation of the renin-angiotensin system by renal ischemia elevates adenosine levels and that adenosine acts in a negative feedback loop to limit renin release and to mitigate some of the hypertension-producing effects of angiotensin II. To further test this hypothesis, we compared the time course of caffeine-induced increases in plasma renin activity with the time course of changes in plasma levels of adenosine in two models of renin-dependent renovascular hypertension. Also, we compared the effects of caffeine on plasma renin activity and arterial blood pressure in renin-dependent versus renin-independent renovascular hypertension. In comparison to sham-operated rats, plasma levels of adenosine in the left and right renal veins and aorta were elevated severalfold in two-kidney, one clip rats (2K1C) 1 week after left renal artery clipping. However, adenosine levels declined during the second and third weeks after clipping. In 2K1C rats treated chronically with caffeine, plasma renin activity was markedly elevated during the first week after operation as compared to non-caffeine-treated 2K1C rats. However, during the second and third weeks after clipping, caffeine had lesser effects on plasma renin activity. A temporal relationship between plasma adenosine levels and caffeine-induced hyperreninemia was also observed in rats with aortic ligation. Caffeine accelerated hypertension in 2K1C rats and rats with aortic ligation (renin-dependent renovascular hypertension), but it had no effect on plasma renin activity or blood pressure in one-kidney, one clip rats (renin-independent renovascular hypertension). These results lend further support to the hypothesis that adenosine functions to mitigate the renin-angiotensin system in renin-dependent renovascular hypertension.

Vectors that facilitate the expression and purification of foreign peptides in Escherichia coli by fusion to maltose-binding protein

Vectors were constructed that allow foreign peptides to be expressed in Escherichia coli as fusion proteins. The peptides are fused to the C terminus of maltose-binding protein (MBP), which allows them to be purified by the MBP's affinity to cross-linked amylose (starch). The fusion protein can be directed to the periplasm by including the leader sequence from the phoA gene on the vector.

The inhibitory effect of somatic inputs on the excitatory responses of vagal cardiomotor neurones to stimulation of the nucleus tractus solitarius in rabbits

Experiments were done in 41 rabbits anaesthetized with urethane and chloralose, paralyzed with Flaxedil and ventilated artificially. Extracellular recordings of 142 units were made in the dorsal vagal nucleus (DVN) and the nucleus ambiguus (NA), identified by antidromic response to stimulation of the cervical vagus nerve. In total 63.5% of them exhibited spontaneous activity and 22 units (17 in DVN and 5 in NA) showed a cardiac rhythm; their antidromic conduction velocity was 3.7-12.5 m/s, which suggests their having axons in the range of B fibres. These neurones were classified as vagal cardiomotor neurones. A total of 16 DVN and 4 NA vagal cardiomotor neurones were excited orthodromically by electrical stimulation of the contralateral nucleus tractus solitarius (NTS). Electrical stimulation of the superficial peroneal nerve (SP) with low intensity or the deep peroneal nerve (DP) with high intensity which activated C fibres inhibited excitatory responses of 16 neurones (14 in DVN and 2 in NA). The other 4 neurones were unaffected by SP inputs. These results provide electrophysiological evidence for the inhibitory effect of somatic inputs on the evoked discharges of vagal cardiomotor neurones in the DVN and the NA.

A possible explanation of genetic hypertension in the spontaneously hypertensive rat

Converting enzyme inhibitors prevent the development of hypertension and normalize arterial blood pressure in spontaneously hypertensive rats (SHR), suggesting a critical role for angiotensin II in genetic hypertension. We hypothesized that the SHR is hyperresponsive to the slow-pressor effect of angiotensin II. To test this hypothesis, 14 SHR and 14 normotensive Wistar Kyoto rats (WKY) were treated chronically with captopril (100 mg X kg-1 X day-1 in drinking water) beginning at 5 weeks of age. At 9 weeks of age, either angiotensin II (125 ng/min; 7 SHR and 7 WKY) or vehicle (7 SHR and 7 WKY) was infused for 2 weeks via an osmotic minipump implanted into the peritoneal cavity. Captopril treatment was maintained and systolic blood pressure was monitored 3 times weekly. Although systolic blood pressure was similar in SHR and WKY infused with vehicle (101 +/- 2 versus 103 +/- 5 mmHg, respectively during the second week), systolic blood pressure in SHR treated with angiotensin II was much greater than systolic blood pressure in WKY treated with angiotensin II (193 +/- 9 versus 132 +/- 11 mmHg, respectively during the second week, p less than 0.001). These results indicate that compared to WKY, SHR are remarkably more sensitive to the slow-pressor effect of chronic, low-dose infusions of angiotensin II. Our results support the hypothesis that the critical genetic defect in SHR is a change in the sensitivity to the slow-pressor effect of angiotensin II.

Enzyme-linked synthetic oligonucleotide probes: non-radioactive detection of enterotoxigenic Escherichia coli in faecal specimens

Synthetic oligonucleotides, complementary to unique sequences in the heat stable enterotoxin gene of Escherichia coli specific for humans, were prepared with a 30-atom spacer arm and a 3' terminal sulfhydryl group which was coupled to bromoacetyl-derivatized alkaline phosphatase. The resulting direct enzyme-linked oligonucleotide probes, containing one enzyme molecule per oligonucleotide, successfully diagnosed enterotoxigenic Escherichia coli in clinical specimens by using a modified colony hybridization method and a colorimetric assay. The procedure is rapid, simple and reliable with a sensitivity equivalent to that using 5'-terminally labelled [32p]-oligonucleotide probes. The results indicate that the enzyme-labelled oligonucleotide probes should be applicable to the routine diagnosis of enterotoxigenic Escherichia coli and possess the potential for the detection of other microbial pathogens.

Caffeine enhances the slow-pressor response to angiotensin II in rats. Evidence for a caffeine-angiotensin II interaction with the sympathetic nervous system

The purpose of this study was to determine if caffeine augments the slow-pressor response to chronic low-dose infusions of angiotensin II (AII) or the rapid-pressor response to acute infusions of AII. AII was infused (125 ng/min i.p.) for 12 d via mini-osmotic pumps in four groups of rats: group I, intact rats not treated with caffeine (n = 9); group II, intact rats treated with caffeine (0.1% in drinking water, n = 9); group III, rats previously sympathectomized with 6-hydroxydopamine, but not treated with caffeine (n = 10); and group IV, rats previously sympathectomized with 6-hydroxydopamine and treated with caffeine (n = 10). Chronic low-dose AII infusions slowly elevated systolic blood pressure in all groups. Caffeine greatly augmented this slow-pressor response to AII in intact animals; however, caffeine failed to enhance AII-induced hypertension in sympathectomized rats. Caffeine pretreatment did not enhance the rapid-pressor response to acute intravenous infusions of AII. We conclude that caffeine augmented the slow-pressor effect of chronic low-dose infusions of AII via a mechanism that involved the sympathetic nervous system.

Cytogenetic studies of four human lung adenocarcinoma cell lines

G-banded karyotypes were analyzed on four human lung adenocarcinoma cell lines, AGZY83-a, LTEP-a1, LTEP-a2, and GLC-82. More than 50 cells were counted and 20-40 cells were karyotyped for each cell line at different passages. The chromosome numbers of cell line AGZY83-a, LTEP-a1, LTEP-a2, and GLC-82 were 53-69, 100-110, 51-56, and 61-63, respectively. Each cell line had a number of markers involving complex chromosome rearrangements. Chromosomal analysis at different passages showed the stability of these cell lines in vitro. It was revealed that the marker chromosomes involving deletions or rearrangements of the short arm of chromosome #1 were present in all the four cell lines with breakpoints at 1p12-1p22.

Extracorporeal enzyme reactors for depletion of phenylalanine in phenylketonuria

Multitubular enzyme reactors with immobilized enzymes were developed to achieve depletion of circulating substrate by extracorporeal means. To act as prototypes, reactors were prepared with immobilized L-phenylalanine ammonia-lyase, an enzyme that metabolizes phenylalanine to trans-cinnamic acid and ammonia without the need for a coenzyme. We report the first application of phenylalanine ammonia-lyase reactors in an extracorporeal circulation system in a patient with phenylketonuria. A phenylalanine level of 1.82 mmol/L (for the last 6 years) decreased to 1.24 mmol/L after 5.5. hours of treatment, without the enzyme entering the circulation. Total phenylalanine depletion from blood and tissue stores was estimated at 1800 mg. The hemodialysis-like procedure proved to be without side effects, specific for phenylalanine, and suitable in the management of pregnant women with phenylketonuria and late-onset hyperphenylalaninemia. The extracorporeal use of enzyme reactors for temporary enzyme replacement represents a new, safe, and effective therapeutic modality.