A Drosophila doublesex-related gene, terra, is involved in somitogenesis in vertebrates

The Drosophila doublesex (dsx) gene encodes a transcription factor that mediates sex determination. We describe the characterization of a novel zebrafish zinc-finger gene, terra, which contains a DNA binding domain similar to that of the Drosophila dsx gene. However, unlike dsx, terra is transiently expressed in the presomitic mesoderm and newly formed somites. Expression of terra in presomitic mesoderm is restricted to cells that lack expression of MyoD. In vivo, terra expression is reduced by hedgehog but enhanced by BMP signals. Overexpression of terra induces rapid apoptosis both in vitro and in vivo, suggesting that a tight regulation of terra expression is required during embryogenesis. Terra has both human and mouse homologs and is specifically expressed in mouse somites. Taken together, our findings suggest that terra is a highly conserved protein that plays specific roles in early somitogenesis of vertebrates.

[Characteristics of high frequency 249 codon mutation of p53 gene in hepatocellular carcinoma in prevalent area of China]

OBJECTIVE

To study the characteristic features of an unique hotspot missense mutation of the 249 codon of p53 gene demonstrated in human hepato-cellular carcinoma(HCC) in a region of high(Qidong) and low (Beijing) exposure to both hepatitis B virus (HBV) and aflatoxin B1 (AFB1) in China.

METHODS

Surgical samples from 97 HCC from Qidong and 22 from Beijing, China, collected in 1994 through 1997, were studied. The 249 codon mutation of p53 gene was detected by PCR followed by HaeIII RFLP analysis and DNA sequencing. Intracellular p53 protein level was determined by immunohistochemical staining.

RESULTS

High mutation rate of 249 codon of p53 gene was consistently found in recent years, with an average of 53.6% (52/97). No such mutation was identified in 22 Beijing HCC collected in the same time period. The genotype of p53 249 codon mutants which showed heterozygous profile was identified to be homozygous in nature following tumor tissue enrichment. Of 21 HCC shown to have 249 codon mutation, 20 exhibited high intranuclear accumulation of p53 protein. p53 protein staining was negative in the surrounding noncancerous hepatic tissue.

CONCLUSION

The high frequency of homozygous mutation of the 249 codon of p53 gene accompanied with p53 protein accumulation provides important enlightenment in the understanding of hepatocarcinogenesis and clinical application of gene therapy and/or immunotherapy for HCC.

Inhibitory effects of 5-hydroxytryptamine microinjection into thalamic nucleus submedius on rat tail flick reflex are mediated by 5-HT2 receptors

Our previous findings indicated that electrical or chemical activation of the thalamic nucleus submedius (Sm) produced significant antinociceptive effects and that these effect were blocked by lesion or depression of the ventrolateral orbital cortex (VLO) or the periaqueductal gray (PAG) suggesting a role of the Sm in modulation of nociception. To further investigate the neurotransmitter mechanism involved in this nociceptive modulatory pathway, we tested the effects of microinjection of 5-hydroxytryptamine (5-HT, 50 mM, 0.5 microl) into Sm on the tail flick (TF) reflex. The results show that a unilateral microinjection of 5-HT into Sm significantly depresses the TF reflex; and that this effect is repeatable and dose-dependent. Furthermore, microinjection of 5-HT2 receptor antagonist cyproheptadine (CPT, 0.3 mM, 0.5 microl) into the same Sm site reverses this 5-HT-evoked inhibition of TF reflex. These results suggest that 5-HT application to the Sm may activate Sm neurons through the 5-HT2 receptors leading to activation of the brainstem descending inhibitory system via the VLO and depression of the nociceptive information at the spinal level.

Positive and negative cis-acting elements are required for hematopoietic expression of zebrafish GATA-1

GATA-1 is a transcription factor required for development of erythroid cells. The expression of GATA-1 is tightly restricted to the hematopoietic lineage. Using transgene constructs containing zebrafish GATA-1 genomic sequences and the green fluorescent protein (GFP) reporter gene, we previously showed that a 5.6-kb enhancer/promoter fragment is sufficient to direct erythroid-specific expression of the GFP. In this study, we used enhancer/promoter fragments containing various deletion and point mutations to further characterize the cis-acting elements controlling tissue-specific GATA-1 expression. We report here the identification of distinct cis-acting elements that cooperate to confer on GATA-1 its hematopoietic expression pattern. A CACCC box, located 142 bp upstream of the translation start codon, is critical for the initiation of GATA-1 expression. A distal double GATA element is required for maintaining and enhancing the hematopoietic expression of GATA-1. The erythroid-specific activity of the GATA-1 promoter is also enhanced by a 49-bp sequence element located 218 bp upstream of the CACCC element and a CCAAT box adjacent to the double GATA motif. Finally, the hematopoietic specificity of the GATA-1 promoter is secured by a negative cis-acting element that inhibits expression in the notochord.

Changes in cardiac ANG II postmyocardial infarction in rats: effects of nephrectomy and ACE inhibitors

We evaluated in rats the time course of changes in cardiac versus plasma ANG I and II postmyocardial infarction (MI) and the effects of nephrectomy and angiotensin-converting enzyme (ACE) inhibitors on the early changes post-MI. Acute coronary artery ligation was induced in conscious rats using the two-stage model, and plasma and cardiac tissue were obtained shortly (6 h, 1 and 3 days) and chronically (1, 4, and 8-9 wk) after MI. In an additional group of rats, bilateral nephrectomy was performed 18 h before the coronary artery ligation, and samples were obtained at 6 h post-MI. Furthermore, in two additional groups of rats, treatment with enalapril and quinapril was started 3 days before the ligation, and samples were obtained at 1 or 3 days post-MI. In these groups of rats, plasma and left ventricular (LV) (infarct and infarct free) ANG I and II were measured by RIA after separation on HPLC. In control rats, plasma ANG I and II showed a clear increase at 6 h post-MI but subsequently only minor increases were observed. In contrast, LV ANG II showed major increases at 6 h and 1 day post-MI, which had returned to normal by 3 days in the infarct-free LV and after 1(-2) wk in the infarct LV. LV ANG I showed a more gradual increase and remained elevated in the infarct up to 8-9 wk. Nephrectomy preceding the MI lowered ANG I and II in plasma but enhanced their increases in the heart at 6 h post-MI. Both ACE inhibitors decreased plasma ANG II associated with large increases in plasma ANG I. They also inhibited the increases in LV ANG II in both the infarct and infarct-free LV at 1 and 3 days post-MI with however no significant increase in LV ANG I. In conclusion, induction of a MI in conscious rats leads to rapid and marked, but only short-lived, increases in cardiac tissue ANG II in both the infarct and infarct-free parts of the LV. Pretreatment with ACE inhibitors, but not nephrectomy, blocks this increase. Local production appears to play a major role in the increases in cardiac ANG II post-MI.

Inhibitory effects of electrical stimulation of ventrolateral orbital cortex on the rat jaw-opening reflex

In previous studies, we have shown that electrically or chemically evoked activation of the ventrolateral orbital cortex (VLO) depresses the rat tail-flick (TF) reflex, and this antinociceptive effect is mediated by the periaqueductal gray (PAG). The aim of the present study was to examine whether electrical stimulation of the VLO could inhibit the rat jaw-opening reflex (JOR), and to determine whether electrolytic lesions of the PAG could attenuate this VLO-evoked inhibition. Unilateral electrical stimulation of the VLO significantly depressed the JOR elicited by tooth pulp or facial skin stimuli, with a mean threshold of 30.5+/-2.3 microA (n=22). Increasing stimulation intensities from 30 to 80 microA resulted in greater reduction of the dEMG amplitude from 22.9+/-5.0% to 69.7+/-3.7% of the baseline value (P<0.01, n=22). The inhibitory effect appeared 50 ms after the beginning of VLO stimulation and lasted about 150 ms, as determined by varying the conditioning-test (C-T) time interval. Unilateral lateral or ventrolateral lesions of the PAG produced only a small attenuation of the VLO-evoked inhibition of the JOR, but bilateral lesions eliminated this inhibition. These findings suggest that the VLO plays an important role in modulation of orofacial nociceptive inputs, and provide further support for the hypothesis that the antinociceptive effect of VLO is mediated by PAG leading to activation of a brainstem descending inhibitory system and depression of nociceptive inputs at the trigeminal level. The role played by VLO in pain modulation is discussed in association with the proposed endogenous analgesic system consisting of medullary cord-Sm-VLO-PAG-medullary cord.

Dietary-sodium-induced cardiac remodeling in spontaneously hypertensive rat versus Wistar-Kyoto rat

OBJECTIVE

To study the effects of short-term and long-term high sodium intake on cardiac mass and design in sodium-sensitive spontaneously hypertensive rats versus sodium-resistant Wistar-Kyoto rats.

METHODS

Young spontaneously hypertensive rats and Wistar-Kyoto rats were randomly allocated to control diet, 2 or 8% dietary sodium for 2-12 weeks and changes in resting hemodynamics, cardiac angiotensin II level, sympathetic activity and cardiac structure evaluated. Sympathetic activity was assessed by measuring levels of plasma catecholamines, responses of blood pressure to ganglionic blockade, and rates of cardiac turnover of norepinephrine.

RESULTS

High sodium intake for 4 weeks increased left ventricle weight of Wistar-Kyoto rats aged 4 weeks (by 11 and 25% for 2 and 8% NaCl diets, respectively). This hypertrophic response was temporary, however, had already diminished after 6 weeks, and was absent after 12 weeks of a high sodium intake. However, after prolonged exposure concentric remodeling occurred (i.e. left ventricle wall thickness : radius ratio increased with no change in left ventricle mass). High sodium intake did not affect resting blood pressure, cardiac index, cardiac angiotensin II level, and general sympathetic activity of Wistar-Kyoto rats. Short-term high sodium intake did not increase left ventricle mass of young spontaneously hypertensive rats, unless sodium intake was so high (8% NaCl) that blood pressure and general sympathetic activity increased, too. However, a prolonged moderate (2%) increase in sodium intake also caused concentric remodeling in spontaneously hypertensive rats without increasing left ventricle mass, blood pressure, cardiac index, and general and cardiac sympathetic activities.

CONCLUSIONS

The blood pressure in young Wistar-Kyoto rats is sodium-insensitive but the heart structure is sodium-sensitive and high dietary sodium intake causes an early hypertrophic response, and then concentric remodeling. In contrast, hypertrophic response appears to occur after the response of blood pressure in spontaneously hypertensive rats, whereas the remodeling is similar to that in Wistar-Kyoto rats.

[Responses of neurons in thalamic nucleus submedius to electrical stimulation of peroneal nerve and "zusanli" point in rats]

The experiments were performed on the anesthetized rats. Single unit was recorded extracellularlly from the thalamic nucleus submedius (Sm) with glass micropipettes. The responses of Sm neurons were examined to electrical stimulation of the peroneal nerve and "Zusanli" point. The results show that most (81%) of the neurons in Sm responded to electrical stimulation of the peroneal nerve with afferent C fiber excitation, and this response increased following increase of the stimulation intensity and pulse numbers. It was found that electrical stimulation of the "Zusanli" point could activate the Sm neuronal activities with higher intensity threshold compared to that of the peroneal nerve stimulation, and the response properties of Sm neurons to acupoint stimuli were similar to those to stimulation of peroneal nerve. These results provide support for the hypothesis that a negative feedback loop consisting of spinal cord-Sm-VLO-PAG-spinal cord responsible for nociceptive modulation is involved in acupuncture analgesia, especially in analgesia produced by electroacupuncture-evoked activation of the afferent C fibers.

[Effects of bilateral lesions of ventrolateral orbital cortex on the rat tail flick reflex inhibition evoked by electroacupuncture]

This study found that bilateral electrolytic lesions of the ventrolateral orbital cortex (VLO) markedly reduced the inhibitory effects of high intensity electroacupuncture (EA) at "Zusanli" point on tail flick reflex in lightly anesthetized rats, but did not influence the inhibitory effects of low intensity EA stimulation. The results show that the VLO is involved in acupuncture analgesia produced by activation of small afferent fibers with high intensity electroacupunture. Results of this study provide further support for a hypothesis that spinal cord-Sm-VLO-PAG-spinal cord may constitute a negative feedback loop of nociceptive modulation. The analgesic effects produced by high intensity electroacupuncture may be mediated by this loop leading to depression of the nociceptive inputs at the spinal cord level.

A region within murine chromosome 7F4, syntenic to the human 11q13 amplicon, is frequently amplified in 4NQO-induced oral cavity tumors

Our previous reports have shown that two thirds of 4-nitroquinoline-1-oxide (4NQO)-induced murine oral squamous cell carcinomas (SCC) have Hras1 mutations. Loss of heterozygosity (LOH) involving the distal portion of chromosome (Chr) 7 occurred in half of the tumors with Hras1 mutations. Here, we demonstrate that five of six tumors with LOH have 4-8-fold amplification involving the distal portion of Chr 7 (7F4). Ccnd1. Fgf4 and Fgf3, within the most telomeric region of Chr 7 (70.5 cM), are co-amplified. The region is syntenic to a previously identified human amplicon at 11q13. Only one out of eight tumors without LOH at Chr 7 had twofold amplification; the other seven had no detectable amplification. Significant amplification is restricted to the chromosome with the Hras1 mutation. Gene amplification occurred without overexpression since only one of five tumors with amplification and one of six tumors without Ccnd1 amplification expressed increased protein. Although amplification of 11q13 occurs rather frequently in human tumors, 4NQO-induced oral cavity tumors in inbred mice are the first example of a murine tumor with consistent amplification. Our observations are strikingly similar to human head and neck SCC where overexpression of genes within the 11q13 amplicon is inconsistently detected. The amplification of genes localized to human 11q13 and the syntenic region on murine Chr 7 during tumorigenesis suggests that similar structural elements are present which predispose these regions to amplification during malignant transformation.

Blockade of brain 'ouabain' prevents the impairment of baroreflexes in rats after myocardial infarction

BACKGROUND

The purpose of this study was to test whether increased brain "ouabain" contributes to impairment of both arterial and cardiopulmonary baroreceptor reflexes in congestive heart failure (CHF).

METHODS AND RESULTS

Two to 5 days after coronary artery ligation (MI) or sham surgery in male Wistar rats, chronic intracerebroventricular (ICV) infusion was started with either antibody Fab fragments, which bind ouabain and related steroids with high affinity, or gamma-globulins as control (200 microg x 12 microL[-1] x d[-1] for both) with osmotic minipumps implanted subcutaneously. After 8 weeks of infusion, in conscious rats, mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), and renal sympathetic nerve activity (RSNA) were recorded at rest and in response to ramp changes in blood pressure (BP) induced by intravenous phenylephrine and nitroprusside and to changes in CVP elicited by acute volume expansion with 5% dextrose. Compared with sham rats, in MI rats with ICV gamma-globulins, resting MAP was significantly lower and CVP increased, and both arterial and cardiopulmonary baroreflex control of RSNA and HR were attenuated. ICV Fab fragments prevented the decrease in resting BP and largely prevented impairment of arterial and cardiopulmonary baroreflex control of both RSNA and HR.

CONCLUSIONS

These data indicate that increased brain ouabain plays a major role in the impairment of baroreflexes in rats with CHF after myocardial infarction.

Inhibitory effects of electrically evoked activation of ventrolateral orbital cortex on the tail-flick reflex are mediated by periaqueductal gray in rats

The present study found in lightly anesthetized rats that the radiant heat-evoked tail flick (TF) reflex was markedly inhibited by a unilateral electrical stimulation (a 20 ms train of 0.2 ms, 100 Hz, 30-100 microA pulses) of the ventrolateral orbital cortex (VLO), with the tail flick latency (TFL) being increased. The mean threshold of VLO stimulation for producing inhibition of the TF reflex was 39.2 +/- 8.7 microA (n = 26), and this inhibitory effect increased following increasing stimulation intensity from 40 to 70 microA. The inhibition developed and remained during the stimulation and disappeared rapidly after termination of the stimulation. When the VLO was stimulated at an intensity of 100 microA in addition to the inhibition an after-facilitation of the TF reflex (a decrease in TFL) was observed at 5-10 s after termination of the stimulation. Bilateral electrolytic lesions of the lateral or ventrolateral parts of the periaqueductal gray matter (PAG) dramatically reduced or eliminated the VLO-evoked inhibition, and the after-facilitation as well. The difference was significant between the TFL changes produced by VLO stimulation before and after PAG lesion (P < 0.01). The results suggest that the antinociception elicited by VLO stimulation is mediated by PAG, leading to activation of the brainstem descending inhibitory system which depresses the nociceptive transmission at the spinal level. The role played by VLO in pain modulation was discussed in association with the proposed endogenous analgesic system consisting of spinal cord-Sm-VLO-PAG-spinal cord.

Genetic analysis of interactions between Gag proteins of Rous sarcoma virus

The yeast two-hybrid system was used to characterize homomeric interactions between the Gag proteins of Rous sarcoma virus (RSV). The RSV Gag precursor was found to interact strongly with itself and not with various control proteins. The RSV Gag did not interact significantly with Gag proteins of a variety of other retroviruses, including murine leukemia viruses and primate lentiviruses. Deletion analysis suggested that two nonoverlapping regions are independently sufficient to mediate RSV Gag-Gag dimerization. One such region lies near the N terminus and contains p2, p10, and a large N-terminal part of the capsid (CA) domain; the other is localized in the C terminus and includes a small C-terminal portion of CA and the nucleocapsid protein. These interaction domains may play roles in viral assembly.

Consistent allelic loss on mouse chromosome 7 distal to tyrosinase in 4-nitroquinoline-1-oxide-induced oral cavity tumors with loss of heterozygosity at Ha-ras-1

We have previously shown that all CBA/J mice exposed to 4-nitroquinoline-1-oxide (4NQO) eventually develop oral cavity squamous cell carcinomas, and two-thirds of these tumors have Ha-ras-1 (Hras1) point mutations at codon 12. Half of the tumors with Hras1 mutations have loss of heterozygosity (LOH) at Hras1. In the study reported here, seven tumors with LOH at Hras1, six heterozygous for Hras1, and six without Hras1 mutations were analyzed to define the extent of LOH on chromosome (Chr) 7. Microsatellite polymorphisms present in CBA/J mice were used as informative allelic markers. Tumors with LOH at Hras1 showed consistent allelic loss at the distal portion of Chr 7. The boundary of allelic loss lay between the tyrosinase and hemoglobin beta chain loci, which are 6 cM apart. None of the tumors that remained heterozygous for Hras1 or had no Hras1 mutations had evidence of chromosomal loss involving Chr 7. Because LOH was only detected in advanced lesions long after exposure to 4NQO had ceased, we presume that the chromosomal alterations by which LOH occurred were independent of the carcinogen exposure. The development of LOH in only half of the tumors with Hras1 point mutations suggests that LOH was not caused by the initial Hras1 point mutation but was a highly selected event during tumorigenesis.

Involvement of the frontal ventrolateral orbital cortex in descending inhibition of nociception mediated by the periaqueductal gray in rats

Our previous findings which indicated that electrical stimulation of ventrolateral orbital cortex (VLO) can depress the rat tail flick (TF) reflex and that the VLO-evoked inhibitory effect is blocked by electrolytic lesions of periaqueductal gray (PAG) suggest a role of the VLO in the modulation of nociception. To further investigate the involvement of VLO in this nociceptive modulatory pathway, we tested the effects of microinjections of glutamate (200 mM, 0.7 microliter) into the VLO on the TF reflex. An unilateral microinjection of glutamate into the VLO significantly depressed the TF reflex; and this effect was repeatable. Furthermore, bilateral microinjections of gamma-aminobutyric acid (GABA: 100 mM, 0.5 microliter on each side) into the ventrolateral parts of PAG could eliminate this VLO-evoked inhibition of the TF reflex. These results, along with our previous findings provide further support for a hypothesis that VLO, as a higher center in the frontal cortex, plays an important role in modulation of nociception, and this role is mediated by PAG leading to activation of the brainstem descending inhibitory system which depresses the nociceptive information at the spinal level.

[Transformation of rat hepatocytes in an in vitro primary culture by aflatoxin B1]

Aflatoxin B1 (AFB1) is one of the major causative factors of hepatocellular carcinoma. In this study, the combined effects of AFB1 activated by human cytochrome p450 IA2 and c-myc in transformation of rat hepatocytes were investigated in an in vitro primary culture system. The expression vectors, Xm-6/c-myc was first constructed and their expression possibilities were examined in Alexander cells by immunocytochemistry. Then both c-myc and human cytochrome p450 IA2 expression vectors were sequentially transfected into newborn rat liver cells in serum-free primary culture. Results showed that p450 IA2 could activate AFB1 at concentrations as low as 5 ng/ml, and the activated AFB1 coupled with exogenous c-myc could induce rat hepatocytes to survive and grow beyond two-month limit in primary culture. During long-term in vitro culturing including four-month in crisis, one of the randomly selected transformed hepatocytes with the growth advantage became immortalized. Immunocytochemical assays for CK-18 and rat albumin plus observed electron microscopic features clearly confirmed these cells derived from epithelial hepatocytes. Further characterization showed that the process of immortalization was associated with chromosomal abnormalities and elevated expression of TGF alpha.

[Metallic elements in boiling water extracts from 3 processed products of concha Aracae]

The results show that the contents of Zn, Mn, Fe, Cu, Ca, Pb et al in the boiling water extracts of calcined and vinegar-quenched products are higher than those of calcined products, the contents of Zn, Mn, Fe, Cu, Ca, Pb etc. in the boiling water extracts of calcined products are higher than those of crude drugs, and the contents of Zn, Cu, Ca, Pb, V, Mn etc. in the boiling water extracts from 3 processed products are higher than those in the digestive juices of boiling water extracts from 3 processed products, but the content of Fe in the boiling water extracts from 3 processed products are lower than that in the digestive juices of boiling water extracts from 3 processed products.

Frequent DNA polymorphisms exist in inbred CBA/J and C3H/HeN mice

Although occasional DNA polymorphisms have been observed in inbred mice, CBA/J and C3H/HeN mice have two microsatellite alleles at over 1/3 of microsatellite loci tested. Since DNA polymorphisms were not detected in DBA/2J, C57BL/6J, and BALB/cJ, the frequency of microsatellite polymorphisms appears to be strain specific. Thus, genetic studies in inbred mice require testing for preexisting polymorphisms. The polymorphisms detected in CBA/J mice appear to be stable and do not represent microsatellite instability or a mutator phenotype. Somatic mosaicism was not observed and no more than two alleles were detected per locus. CBA/J propagated only by brother-sister mating maintained seven of eight polymorphisms over 5 years. These data suggest that the polymorphisms are due to an inherited trait and that the pattern of inheritance is not due to Mendelian distribution. As breeding analysis was not performed, the pattern of allelic inheritance is unknown.

Inhibitory effects of electrical stimulation of thalamic nucleus submedius on the nociceptive responses of spinal dorsal horn neurons in the rat

The aim of the present study is to examine whether stimulation of the thalamic nucleus submedius (Sm) exerts an inhibitory influence on the long latency responses (C-responses) of the spinal cord dorsal horn neurons evoked by noxious cutaneous electrical stimulation, in an attempt to provide electrophysiological evidence for involvement of the Sm in modulation of nociception. Single unit extracellular recordings from the dorsal horn neurons were obtained with glass micropipettes in pentobarbital-anesthetized rats. A total of 71 nociceptive neurons, including 61 wide dynamic range (WDR) and 10 nociceptive specific (NS) neurons, were studied in 29 rats. Electrical stimulation of either ipsilateral or contralateral Sm markedly suppressed the C-responses in most (75%, 53/71) of these neurons, and facilitated the responses in only a few neurons. In general, the inhibitory effect was dependent on both the stimulus intensity and the length of stimulus train, and the stimulus threshold for the inhibition to be elicited was about 50 microA when a 300-ms train of 0.2-ms pulses at 200 Hz was used. The inhibitory effect outlasted the Sm stimulation about 500 ms. Inhibition of C-responses could also be produced by stimulation of the dorsal hypothalamic area (DA). On the other hand, stimulation of the structures in the medial thalamus surrounding Sm had no obvious influences on the C-responses of the dorsal horn neurons. The findings of this study provided further support for the hypothesis that Sm may be implicated in the descending modulation of nociception.

Homomeric interactions between transmembrane proteins of Moloney murine leukemia virus

We have studied homomeric interactions between transmembrane proteins (TM) of the Moloney murine leukemia virus envelope using the Saccharomyces cerevisiae two-hybrid system. TM interacts strongly with itself but not with various control proteins. Deletional and mutational analyses indicated that the putative leucine zipper motif in the extracellular domain of TM is essential and sufficient to mediate the binding. The first three repeats of the leucine zipper-like motif are the most important in mediating the interaction. The TM-TM interaction detected in this system may play a role in several stages of viral replication.

Brain 'ouabain' mediates sympathetic hyperactivity in congestive heart failure

In congestive heart failure (CHF), endogenous compounds with ouabainlike activity (OLA) may contribute to the maintenance of the circulatory homeostasis by peripheral as well as central effects. In the present study, we assessed changes in peripheral (plasma and left ventricle) and central (pituitary, hypothalamus, pons, and cortex) OLA in two animal models of CHF and determined whether brain OLA mediates sympathetic hyperactivity in CHF. Cardiomyopathic hamsters with their controls were studied at 9 months of age for tissue OLA. Rats were studied 4 weeks after acute coronary artery ligation for tissue OLA and sympathetic activity. In both models, left ventricular end-diastolic pressure was markedly increased. CHF was associated with significant increases in both plasma and tissue OLA in both models. In the brain, the most marked (twofold to threefold) increases occurred in the hypothalamus. In vitro, all OLA measured could be blocked by antibody Fab fragments (Digibind). Conscious rats with CHF showed elevated plasma catecholamines and enhanced responses of mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) to air stress and to intracerebroventricular (ICV) injection of the alpha 2-adrenergic receptor agonist guanabenz compared with sham-operated rats. ICV administration of the Fab fragments did not change resting RSNA or responses to air stress at 1 hour. However, 18 hours after injection of the Fab fragments, resting RSNA levels had significantly decreased compared with the control values, and plasma catecholamine levels had decreased to control values.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of electrical stimulation of thalamic nucleus submedius area on the rat tail flick reflex

This study in lightly anesthetized rats found that unilateral electrical stimulation delivered to the ventral part of the thalamic nucleus submedius (Sm), the thalamic reuniens nucleus (Re) and the hypothalamic dorsal area (DA) markedly depressed the TF reflex, and this inhibitory effect increased following increasing stimulation intensity. Stimulation in the dorsal part of Sm did not produce any or only slight depression of the TF reflex. Furthermore, an ipsilateral electrolytic lesion of the ventrolateral orbital cortex (VLO) eliminated the unilateral Sm-evoked inhibition, but not the inhibition elicited by Re and DA and contralateral Sm stimulation. Finally, after bilateral electrolytic lesions of the ventrolateral periaqueductal gray (PAG) the DA and Re and contralateral Sm-evoked inhibitions were also eliminated. The results suggest that the Sm plays an important role in modulation of nociceptive inputs, and this role of Sm is mediated by the VLO and leads to activation of the PAG descending inhibitory system and depression of the nociceptive inputs at the spinal cord level.

[The roles of thalamic nucleus submedius in nociception and pain modulation]

Recent studies on the roles of thalamic nucleus submedius (Sm) in nociception and pain modulation were reviewed in this article in combination with own our works. Results of these studies showed that Sm may be involved in effective-motivational aspects of pain, and that Sm-VLO-PAG may constitute a pathway of nociceptive modulation which may depress the nociceptive inputs at the spinal cord level via the brain-stem descending inhibitory system, thereby mediate a negative feedback regulation of pain.

Effects of thalamic nucleus submedius lesions on the tail flick reflex inhibition evoked by hindlimb electrical stimulation in the rat

Bilateral electrolytic lesions of the thalamic nucleus submedius (Sm) facilitated the TF reflex and attenuated the antinociception evoked by hindlimb electrical stimulation with high intensities in lightly anaesthetized rats. However, the antinociception produced by low intensity hindlimb stimulation was unchanged, except that the after-effect was reduced. The results show that the Sm is probably involved in pain modulation and plays an important role in mediation of the antinociception elicited by high intensity peripheral stimulation.

Harvey ras (H-ras) point mutations are induced by 4-nitroquinoline-1-oxide in murine oral squamous epithelia, while squamous cell carcinomas and loss of heterozygosity occur without additional exposure

Tumorigenesis is a multistep genetic process requiring several somatic mutations for neoplastic transformation. These mutations appear to be sequential, random, and independent events. However, we find linked, nonrandom ras mutations occurring during 4-nitroquinoline-1-oxide-induced tumorigenesis months after exposure to the carcinogen had ceased. The carcinogen had been topically applied to the oral cavity of CBA mice for 4 to 16 weeks. Dysplasia developed after 24 weeks, and carcinoma in situ and squamous cell carcinoma developed after 28 weeks. H-ras mutations were detected in 13 of 25 tissue specimens (10 of 14 invasive carcinomas and 2 of 4 carcinoma in situ, 1 of 5 dysplastic tissue, and 0 of 2 normal tissues). Approximately one-half of the tumors had G to A point mutations at codon 12 of the cellular H-ras proto-oncogene on mouse chromosome 7. None had codon 11, 13, or 61 mutations. Loss of heterozygosity occurred in 5 of 14 invasive cancers. Larger invasive squamous cell carcinomas consistently lost the wild-type allele, whereas preneoplastic lesions and small tumors were heterozygous for ras. This suggests a causal relationship between carcinogen treatment, H-ras activation, and initiation of tumorigenesis. The wild-type allele in mouse chromosome 7 is lost with the progression of tumorigenesis long after exposure to the carcinogen. Thus, loss of heterozygosity of the ras gene appears to occur without multiple carcinogen-induced mutations, i.e., as a result of a cascade of events induced by an earlier ras mutation.

Posttransplantation plasma cell dyscrasias

BACKGROUND

Lymphoproliferative disorders that occur in patients receiving cyclosporine for immunosuppression after solid organ transplantation typically are B-cell neoplasms associated with Epstein-Barr virus (EBV), which may be polyclonal or monoclonal in origin. Although these tumors may have partial B-cell differentiation, (manifested as plasmacytoid features), terminal differentiation to plasma cells that secrete a monoclonal immunoglobulin is rare. The case of a patient who developed a posttransplantation lymphoproliferative disorder that was composed of multiple plasmacytomas located in the abdomen and urinary bladder after liver transplantation is presented. The patient also had high levels of an immunoglobulin-G kappa monoclonal paraprotein.

METHODS

The plasmacytoma was examined for the presence of EBV by both polymerase chain reaction and in situ hybridization, and the possibility of a codon-12 mutation in the ras gene was investigated by digestion of DNA amplification products with the HpaII-restriction endonuclease.

RESULTS

Epstein-Barr virus genomes were demonstrated by DNA amplification of sequences in the long, internal, direct repeat region, and in situ hybridization showed expression of EBV RNA transcripts that annealed to an EBER-1 probe. Immunohistochemistry showed clonally restricted expression of kappa light chains but failed to reveal evidence of expression of the latent membrane protein 1 encoded by EBV. Mutations of codon-12 in the H-ras gene were not detected.

CONCLUSIONS

Resolution of the tumor and the paraprotein after radiation and reduction of immunosuppression indicates that terminal plasmacytic differentiation does not necessarily portend an unfavorable prognosis, even in a clonal lesion.

Effects of enalapril versus losartan on regression of volume overload-induced cardiac hypertrophy in rats

BACKGROUND

The role of nonhemodynamic cardiac trophic mechanisms differs not only between different models of cardiac hypertrophy but also within the same model for development versus maintenance of cardiac hypertrophy. Our previous studies pointed to a major role for the renin-angiotensin system (RAS) as a cardiac trophic stimulus in the remodeling of the heart in response to volume overload by aortocaval shunt or minoxidil treatment.

METHODS AND RESULTS

In the present study, we evaluated the effects of blockade of the RAS by the angiotensin-converting enzyme inhibitor enalapril and the angiotensin II receptor blocker losartan on left ventricular (LV) and right ventricular mass and LV dilation in relation to changes in central hemodynamics during the maintenance of minoxidil and aortocaval shunt-induced cardiac hypertrophy. Both blockers similarly decreased LV end-diastolic pressure (LVEDP) and LV peak systolic pressure, whereas cardiac output remained unchanged in both models of volume overload. This suggests a major contribution of improved LV performance and decreased afterload to the decrease in cardiac preload by the two blockers rather than decreased venous return. Both blockers reversed LV hypertrophy in parallel to their effects on LVEDP in both models of volume overload. In minoxidil-treated rats, the extent of reversal in LV mass and dilation by the two blockers was similar to "spontaneous regression" after discontinuation of minoxidil treatment.

CONCLUSIONS

These results indicate that in contrast to the development phase of cardiac hypertrophy, the RAS does not contribute to the maintenance of volume overload-induced cardiac hypertrophy in these two models via direct cardiac trophic effects. The RAS, however, maintains cardiac hypertrophy indirectly by contributing to the persistence of high filling pressures.

[Descending pathways mediating the effect of stimulating cerebral peduncle on the spinal nociceptive transmission in the rat]

The descending pathways for the effects of stimulation of cerebral peduncle (CP) on the nociceptive neurons of spinal cord dorsal horn were analyzed by subtotal spinal cord lesions in anesthetized rats. Inhibition was the predominant effect of CP stimulation on the C-fiber elicited nociceptive responses of dorsal horn neurons, in 30.7% of such neurons, the inhibition was preceded by some initial excitation. In most neurons the inhibitory effect was mediated by both dorsal funiculus (DF) and dorsolateral funiculus (DLF), that of DF usually predominated. It seemed that DLF played a more important role than DF. However, the excitatory effect was mediated by DF alone. Since in the rat the corticospinal tract (CST) is situated in the DF, the results suggest that cerebral cortex can modulate spinal nociceptive transmission not only by the CST, but also through a relay in some supraspinal structure(s) sending descending fibers into the DLF.

Exploration of requirements for peptide binding to HLA DRB1*0101 and DRB1*0401

The individual amino acid contacts responsible for peptide binding to DRB1*0101 and/or DRB1*0401 were defined using a quantitative binding assay. The differential contribution of each amino acid in two well studied T cell determinants, HA307-319 and RMBP 90-102, was delineated by comparing the IC50 values of analogues of varying length. This analysis confirmed the importance of a hydrophobic amino acid located near the amino-terminus for binding to both alleles and revealed that the contribution of the carboxyl-terminal amino acids differed between DRB1*0101 and DRB1*0401. Taking advantage of previous experiments demonstrating that all of the residues could be replaced with alanine, with the exception of the key hydrophobic amino acid, simplified analogues composed of polyalanines were used to prove 1) optimal binding depended on the position of the hydrophobic side chain relative to the amino- and carboxyl-termini; 2) aromatic amino acids were superior to aliphatic side chains at this position; and 3) a significant amount of free energy of binding arises from hydrogen bonding between the class II binding site and the amide bonds of the ligand. The role of each carbonyl and amide nitrogen was measured by assaying analogues containing reduced peptide bonds or N-methyl amino acids. Serine, but not glycine, could be used as a framework amino acid for peptide ligands, indicating that the beneficial aspects of these simplified structures was the combination of retaining the correct orientation of the peptide bonds, the restriction of the conformational freedom by limiting the possible phi/psi angles of the peptide, and avoidance of deleterious side-chain contacts. Collectively, these data were consistent with the peptide binding in a nonrepeating conformation with the vast majority of the free energy of binding arising from hydrogen bonds with the peptide backbone and a single, key hydrophobic side chain interacting in a conserved pocket in both DRB1*0101 and DRB1*0401.

Exploration of requirements for peptide binding to HLA DRB1*0101 and DRB1*0401

The individual amino acid contacts responsible for peptide binding to DRB1*0101 and/or DRB1*0401 were defined using a quantitative binding assay. The differential contribution of each amino acid in two well studied T cell determinants, HA307-319 and RMBP 90-102, was delineated by comparing the IC50 values of analogues of varying length. This analysis confirmed the importance of a hydrophobic amino acid located near the amino-terminus for binding to both alleles and revealed that the contribution of the carboxyl-terminal amino acids differed between DRB1*0101 and DRB1*0401. Taking advantage of previous experiments demonstrating that all of the residues could be replaced with alanine, with the exception of the key hydrophobic amino acid, simplified analogues composed of polyalanines were used to prove 1) optimal binding depended on the position of the hydrophobic side chain relative to the amino- and carboxyl-termini; 2) aromatic amino acids were superior to aliphatic side chains at this position; and 3) a significant amount of free energy of binding arises from hydrogen bonding between the class II binding site and the amide bonds of the ligand. The role of each carbonyl and amide nitrogen was measured by assaying analogues containing reduced peptide bonds or N-methyl amino acids. Serine, but not glycine, could be used as a framework amino acid for peptide ligands, indicating that the beneficial aspects of these simplified structures was the combination of retaining the correct orientation of the peptide bonds, the restriction of the conformational freedom by limiting the possible phi/psi angles of the peptide, and avoidance of deleterious side-chain contacts. Collectively, these data were consistent with the peptide binding in a nonrepeating conformation with the vast majority of the free energy of binding arising from hydrogen bonds with the peptide backbone and a single, key hydrophobic side chain interacting in a conserved pocket in both DRB1*0101 and DRB1*0401.

Arterial hypertrophy and pressor responsiveness during development of hypertension in spontaneously hypertensive rats

BACKGROUND

In contrast to studies in isolated blood vessels, results from whole-animal studies are ambiguous regarding differences in pressor responsiveness between spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats, possibly related to the measurement of blood pressure instead of total peripheral resistance (TPR) and to differences in compensatory mechanisms.

OBJECTIVE AND DESIGN

We evaluated responses of blood pressure and TPR to two doses of the alpha 1-agonist phenylephrine during the development of hypertension and cardiovascular hypertrophy in SHR aged 8-26 weeks compared with age-matched WKY rats before and after ganglionic blockade. At 16 weeks of age more-complete dose-response curves to the alpha 1-agonist methoxamine were also constructed.

RESULTS

Over the age range studied, the SHR developed marked hypertension, related to a significant rise in TPR, and concomitantly significant cardiac hypertrophy, as well as hypertrophy of the mesenteric arterial bed. The blood pressure responses to phenylephrine were diminished in the SHR compared with the WKY rats at all ages studied, but this effect was significant only in the absence of ganglionic blockade. TPR responses were significantly less in the SHR than in the WKY rats, both with and without concomitant ganglionic blockade. In contrast, both blood pressure and TPR responses to low doses, but not higher doses, of methoxamine were enhanced in the SHR compared with the WKY rats.

CONCLUSION

These results indicate that the development of hypertension in SHR in vivo is associated with variable changes in blood pressure and TPR responses to alpha 1-receptor stimulation, depending on the alpha 1-agonist employed.

Dietary sodium stimulates ouabainlike activity in adrenalectomized spontaneously hypertensive rats

Both the adrenal glands and the hypothalamus have been proposed to produce compound(s) with ouabainlike activity (OLA). To evaluate the contribution of the adrenal glands, 4-wk-old spontaneously hypertensive rats (SHR) were sham operated or adrenalectomized. The adrenalectomized SHR were given daily injections of corticosterone and aldosterone. Subsequently, rats were randomized to control or high (8%) dietary Na+, and after 2.5 wk, blood pressure and OLA in plasma, hypothalamus, and pituitary were evaluated. Hypertension developed somewhat less in adrenalectomized vs. sham-operated SHR. On control Na+ intake, adrenalectomy caused only minor decreases in circulating and central OLA. Adrenalectomy did not prevent the 50-90% increases in plasma, hypothalamus, and pituitary OLA caused by high Na+ intake for 2.5 wk. These findings are consistent with the concept that, at least in SHR, the central nervous system may represent the major source of both central and peripheral OLA.

The renin-angiotensin system and volume overload-induced cardiac hypertrophy in rats. Effects of angiotensin converting enzyme inhibitor versus angiotensin II receptor blocker

BACKGROUND

The degree of cardiac hypertrophy is not only load dependent: Among other factors, the renin-angiotensin system may play a role in the regulation of cardiac myocyte growth.

METHODS AND RESULTS

To evaluate the role of the renin-angiotensin system in volume overload-induced cardiac hypertrophy, we assessed: 1) the time course of changes in cardiac hemodynamics, cardiac anatomy, and plasma and cardiac renin activity in response to volume overload induced by two sizes of abdominal aortocaval shunt and 2) the effects of chronic treatment with an angiotensin converting enzyme inhibitor (ACEI) versus an angiotensin II receptor blocker on hemodynamics and cardiac hypertrophy. Drug treatment started 3 days before shunt surgery. An increase in left ventricular end-diastolic pressure (LVEDP) and the development of right ventricular (RV) and left ventricular (LV) eccentric hypertrophy in response to volume overload occurred within the first week after induction of the shunt. Plasma renin activity (PRA) and cardiac renin activity peaked shortly after induction of the shunt. During the chronic phase, LVEDP and PRA decreased somewhat but remained significantly elevated up to 7 weeks after shunt surgery. Cardiac renin activity returned toward normal within 4 weeks after surgery. Treatment with the ACEI enalapril caused only a modest decrease in LV internal diameter but did not affect increases in LV and RV weights in response to volume overload despite a major decrease in LVEDP after chronic treatment. In contrast, treatment with the angiotensin II receptor blocker losartan, which had similar effects on cardiac and peripheral hemodynamics, prevented dilation of the LV after 7 days and attenuated the dilation of the LV after 28 days. Moreover, increases in LV and RV weights were significantly attenuated by losartan.

CONCLUSIONS

The development of volume overload-induced cardiac hypertrophy is associated with significant increases in PRA and cardiac renin activity shortly after induction of an aortocaval shunt. Whereas the two blockers of the renin-angiotensin system decreased LVEDP to a similar extent, only the angiotensin II receptor blocker blunted the hypertrophic response of the heart to volume overload, which is indicative for other than hemodynamic determinants of the cardiac hypertrophic response. One trophic factor may be cardiac angiotensin II generated via an angiotensin II-forming enzyme resistant to ACEI and possibly activated by cardiac volume overload.

[Effects of stimulation of SI cortex and cerebral peduncle on the nociceptive responses of spinal dorsal horn neurons in the rat]

Single spinal dorsal horn neurons were recorded extracellularly with glass micropipettes, and the effect of stimulation of SI cortex or cerebral peduncle (CP) was observed on the long latency discharges (C-fiber evoked response) of the wide dynamic range (WDR) neurons induced by intense electrical skin stimulation. Inhibition was the predominant effect of SI cortex stimulation on the C-fiber evoked responses of WDR neurons. The effect of CP stimulation was similar to that of SI cortex stimulation, except that the former was much more effective than the latter. The inhibition lasted a period of time varying from 400 ms to more than 10 min after CP stimulation in different neurons. Systemic naloxone had no significant effect on the inhibition produced by CP stimulation. Systemic methysergide reduced or eliminated the inhibition in a part of the neurons tested, suggesting that 5-HT, but not opioid peptides, is involved partially in mediation of the descending inhibitory effect originating from the cortex.

Dietary sodium restriction and pressor responsiveness to tyramine in spontaneously hypertensive rats

OBJECTIVE

To determine in vivo whether in young spontaneously hypertensive rats (SHR) dietary sodium restriction decreases adrenergic transmitter release from the sympathetic nerve terminal.

DESIGN

Dietary sodium restriction was initiated in young and mature SHR and Wistar-Kyoto (WKY) rats, and subsequently changes in pressor responsiveness to norepinephrine and to the indirectly acting sympathomimetic tyramine were determined in relation to their effects upon plasma catecholamines.

RESULTS

In young SHR sodium restriction for 3-6 weeks prevented the development of hypertension, whereas in mature SHR sodium restriction did not affect blood pressure. Sodium restriction caused modest decreases in pressor responsiveness to the exogenous alpha-agonist, not different in young and mature SHR compared with WKY rats. In contrast, sodium restriction markedly inhibited pressor-responses to tyramine in young SHR and WKY rats, but not at all in mature rats. Tyramine increased plasma norepinephrine 5-10-fold. However, sodium restriction did not affect this response. The pressor response to tyramine was related to increases in total peripheral resistance, with minimal changes in cardiac output, and could be blocked by alpha 1-receptor blockade in rats on either control or low-sodium diets.

CONCLUSIONS

These results show that sodium restriction causes only a small decrease in the pressor response to norepinephrine, but a more marked inhibition of the pressor response to tyramine in young SHR and WKY rats without affecting the plasma norepinephrine response to tyramine. These results suggest that dietary sodium can indeed affect presynaptic functions in vivo, but that plasma norepinephrine responses to tyramine may not reflect changes in arterial norepinephrine release, or that sodium restriction affects a co-transmitter rather than norepinephrine release per se.

Dietary sodium and the antihypertensive effect of nifedipine in spontaneously hypertensive rats

To assess the interaction of dietary sodium and the antihypertensive response to a calcium antagonist, spontaneously hypertensive rats (SHR) were given a diet of regular or increased (120 v 342 mumol Na+/g food) sodium intake from 4 until 16 weeks of age. Nifedipine was added at 10 weeks of age. This level of sodium intake did not enhance the development of hypertension in SHR. In rats with the regular sodium intake, nifedipine caused only a minor decrease in blood pressure. In contrast, with increased sodium intake nifedipine caused a marked antihypertensive response, preventing the rise in blood pressure occurring between 10 and 16 weeks of age. This enhanced response was associated with a diminished blood pressure fall from ganglionic blockade. These results indicate that modest increases in sodium intake enhance the blood pressure response to a calcium antagonist possibly by potentiating its inhibitory effects on sympathetic activity.

A method for rapid screening of recombinant proteins for recognition by T lymphocytes

A simple, cost-effective method is described that allows rapid screening of recombinant protein sequences for their ability to stimulate T cells. Individual microcultures of E. coli each expressing a gene product or peptide sequence fused to protein A are grown in 96-well plates. Following lysis of the bacteria, the fusion peptide is readily captured with immobilized immunoglobulin in tissue culture wells. No further purification is required. T lymphocytes plus appropriate antigen-presenting cells are added directly to the wells and assayed for proliferation. The DNA in bacteria from wells stimulating T cell proliferation is then sequenced. The technique allows rapid mapping of T cell epitopes by facilitating screening of truncation mutants without extensive purification. Described here is a further application of the technique to study monosubstituted analogues of a known T cell epitope.

Role of the deep mesencephalic nucleus in the antinociception induced by stimulation of the anterior pretectal nucleus in rats

The present study showed that the inhibitory effect on the tail-flick reflex (TF) of stimulating the deep mesencephalic nucleus (DpMe) was very similar to that produced by stimulation of the anterior pretectal nucleus (APtN). An electrolytic lesion of the ipsilateral DpMe greatly reduced the inhibitory effect of APtN stimulation on the TF. Furthermore, activating the neuronal cell bodies in DpMe but not the fibers of passage by microinjection of L-glutamate into this area was also shown to elicit inhibition of TF. On the other hand, inhibiting the neuronal cells in DpMe by microinjection of gamma-aminobutyric acid produced a marked reduction in the APtN-induced inhibition of TF, which was comparable to that produced by DpMe lesions. It is suggested that the APtN-induced antinociception is, at least in part, mediated via a relay through the DpMe.

Chronic arterial vasodilation, central hemodynamics, and cardiac hypertrophy in spontaneously hypertensive rats

To determine the possible contribution of cardiac volume overload in the failure of arterial vasodilators to induce regression of left ventricular hypertrophy (LVH), we evaluated in spontaneously hypertensive rats (SHRs) the changes in central hemodynamics caused by treatment with hydralazine or minoxidil. Cardiac output measured by the thermodilution technique and filling pressures were measured in conscious, freely moving rats. Increases in cardiac output were observed after 1 day of treatment, and persisted during chronic treatment; ganglionic blockade did not affect this increase. However, the LV end-diastolic pressure and right atrial pressure of SHRs were not increased by hydralazine or minoxidil. Minoxidil increased the LV weight, and decreased the LV wall thickness to LV internal radius ratio, whereas hydralazine did not change these parameters. We conclude that in SHRs changes in filling pressures do not represent the primary stimulus for the persistence or progression of cardiac hypertrophy during chronic arterial vasodilation.

Electrohydraulic-clamshell heart with energy converter inside the compliance reservoir

Two new ideas on the electrohydraulic actuation of blood pumps have been combined. The first idea was to put the energy converters that propel the hydraulic fluid inside the compliance reservoir instead of having them separate. Compactness of the device and better cooling of the energy converter by the surrounding fluid are two major advantages of this approach. Secondly, we put the pumping membrane inside a clamshell that fits over a soft ventricle (1). The ventricle can be implanted first, after which the shell is slid over it. These two ideas have resulted in devices described in this paper. Preliminary in vitro and in vivo data are presented.

Dietary sodium restriction and the development of two-kidney, one-clip hypertension in young versus adult rats

To determine the effects of moderate versus severe dietary sodium restriction on the development of 2-kidney, 1-clip (2K,1C) hypertension, young male Wistar rats were placed on diets containing 9, 26, or 101 (control) mumol sodium/g food. Three days later, a solid silver clip (i.d. 0.20 mm) was placed on the left renal artery and diets were continued up to 6 weeks. Adult rats received a 0.25-mm clip. In young clipped rats receiving the 101 mumol/g diet, blood pressure (BP), plasma renin activity (PRA), and BP response to captopril were increased as early as 1 week after clipping and increased further over time. Moderate sodium restriction (26 mumol sodium/g) led to only a slight delay in the development of hypertension; the levels of BP and PRA, the BP response to captopril, and the extent of cardiac hypertrophy achieved by 6 weeks were not different between the 2K, 1C rats receiving 26 or 101 mumol sodium/g. Sodium restriction to 9 mumol/g decreased rate of growth and completely prevented the rise in BP and in left ventricular weight. At 3 and 6 weeks the severely sodium-restricted rats had significantly higher PRA levels than the 2K, 1C control group. However, the BP response to captopril was attenuated relative to the other hypertensive groups. In adult rats, this level of sodium restriction had a small, but significant effect on body weight, but still prevented the increase in BP and in left ventricular weight. In conclusion, dietary sodium restriction can prevent the development of 2K,1C hypertension in both young and adult rats, but only if the restriction is severe. This effect may relate to a marked reduction in the pressor effectiveness of the renin-angiotensin system by low sodium intake per se or by associated metabolic or other changes.

Inactivity of acrylonitrile epoxide to modify a Ha-ras DNA in a non-focus transfection-transformation assay

The transforming potential of acrylonitrile epoxide (ANO) was tested in a modified NIH3T3 transfection-transformation assay. This involves a new ras construct obtained by ligating a human c-Ha-ras-1 proto-oncogene to the pSV2neo mammalian vector. The new plasmid was allowed to react with ANO or an established carcinogen in vitro, and the modified ras DNA transfected into NIH 3T3 cells. The transfectants are subjected to triple selections: G418 (neomycin) resistance, low serum growth, and limit dilutions. The end points are scored by cell growth kinetics and monolayer saturation density. In using this protocol, the EJ tumor ras plasmid was the positive control, and anti-benzo[a]pyrene-7,8- dihydrodiol-9,10-epoxide (anti-BPDE) and N-methyl-N-nitrosourea were found to be positive in yielding transformants. Although ANO-modified ras gave rise to two G418R clones, both were scored negative due to their normal growth rate and monolayer density similar to the negative controls. Southern blot analysis of anti-BPDE transformant DNA revealed a fragment of 411 bp, indicating a ras mutation at codon 11 or 12. However, both the ANO clones showed the wild-type band of 355 bp by the same method.

Concept of a soft, compressible artificial ventricle under evaluation

This study was designed to compare the relative merits of soft and rigid artificial ventricles. A cascade mock circulation was used to measure cardiac output under different circumstances. The data show that these soft air driven ventricles show a Starling's-like response over a wider range of filling pressures than identical, but rigid, ventricles. Compression of soft ventricles by high intrathoracic pressures was simulated in vitro. Air pressures up to +20 mm Hg did not seriously affect soft ventricles. Cardiac tamponade was simulated by compressing the ventricle in a closed fluid compartment. Tamponade became severe when volume reduction of the ventricle rose to 60 ml. Hemolysis caused by soft and rigid ventricles was tested in a blood bag set-up and was 48-82% higher in the rigid ventricle, depending on the driving conditions. Possibly, this could be explained by the authors' finding that rigid ventricles showed a 20% higher intraventricular dP/dtmax value than soft ventricles. Soft ventricles were implanted in three calves as a total artificial heart (TAH). Implantation without quick connectors was easy because the surgeon could easily fold and compress the ventricles. No physiological complications of softness were observed. Blood damage in the animals was low (less than 5 mg/dl). The authors conclude that soft ventricles show distinct surgical and functional advantages over rigid ventricles.

Development of a new inflow valve for a 20cc semisoft ventricle: preliminary results

We remodeled and tested our semisoft 20cc ventricle and made a new bileaflet flap inflow valve. Housings, bases, outflow valve, and a newly designed diaphragm were all made by vacuum forming and put together by radiofrequency welding or glue. In vitro, the ventricle produced a cardiac output of 2.5 to 3.0 L/min and showed reliable durability results. Hematological testing showed no important thrombogenicity of the new valve. Cardiac output was higher than expected for the volume of the ventricle, perhaps because of stretching or flow through. Animal experiments with the left ventricular assist device (LVAD) version was done at Ohio State University. Earlier in Utah, we did 20 cc total artificial heart (TAH) implantations and LVAD experiments in lambs and recently in calves with the 60cc TAH version. A soft ventricle is easy to implant and low in production costs.

Soft artificial ventricles for infants and adults, with or without a clamshell

The quick connect system and mechanical disk valves used in total artificial hearts (TAH) are sources of thrombogenesis and blood damage. Our soft TAH, which has no quick connectors, can be squeezed and bent, making it easily implantable, and blood damage is reduced by the use of trileaflet and biflap polyurethane valves. The soft ventricles were made by vacuum forming, after which the pieces were welded together by radiofrequency heat sealing. A rapid clamshell can be pushed and slipped over the soft heart to prevent deformation of the ventricle. Three calves have had the 60 cc soft TAH implanted, both with and without a clamshell. The cardiac outputs were as high as 7 L/min, without a vacuum applied during diastole. Two lambs received the 20 cc TAH (as an acute experiment); it fit and functioned well. One healthy lamb received a 20 cc left ventricular assist device (LVAD) with a pulsating artificial atrium as a survival experiment. The lamb survived for 8 days, after which the device was removed and the lamb returned to the meadow. Thrombosis in the TAH was minimal, and the plasma free hemoglobin values in all the TAH and LVAD experiments were usually lower than 5 mg/dl and often lower than 2 mg/dl.

New polyurethane valves in new soft artificial hearts

This article describes new bistable valves, and introduces a new soft heart that is easy to implant. Earlier, five polyurethane (PU) valves were implanted in the mitral position in sheep. All five survived for 1 year or more, and the valves, although calcified, were intact. Since the opening resistance was somewhat high, valves that are bistable were developed, which means they may be open or closed. These valves have lower opening resistance, and regurgitation is similar to that of mechanical valves. Eight calves have been implanted with a new, soft total artificial heart (TAH). Seven had bistable leaflet valves; the eighth had mechanical (Bicer) valves in the inflow position. Four of the calves were sacrificed after 22 to 43 days. At autopsy, the number of thromboemboli found, particularly in the kidneys, was low compared with previous experiments. None of these animals received anticoagulants other than the heparin given during heart/lung bypass.

The role of aluminum in the pathogenesis of anemia in an outpatient hemodialysis population

Anemia is a well-defined complication of aluminum overload in chronic dialysis patients which may be present before other manifestations of aluminum toxicity are obvious. Causes of anemia in chronic renal failure are multiple, and at the present time there is no marker for aluminum-induced anemia. Deferoxamine (DFO) treatment can correct aluminum-related anemia and microcytosis, but may be associated with side effects. Because of the possible role of aluminum in red blood cells in causing the anemia associated with aluminum overload, we attempted to test red blood cell (RBC) aluminum as a marker for aluminum-associated anemia and to assess the prevalence of aluminum-associated anemia in an outpatient dialysis population. Both random plasma aluminum and RBC aluminum correlated well with the increase in plasma aluminum seen following DFO challenge. However, RBC aluminum was affected less by changes in oral aluminum intake than plasma aluminum. There were strong correlations of RBC and plasma aluminum to corpuscular volume (MCV) in our patients. Moreover, patients within the highest quartile of RBC aluminum had a lower mean MCV (82.1 +/- 1.7 vs 89.6 +/- 1.7, p less than .01) and hematocrit (HCT) (24.3 +/- 4 vs 28.2 +/- 1.5, p less than .05) than those within the lowest quartile. These data suggest that aluminum toxicity is an important cause of microcytic anemia in outpatient hemodialysis patients. Prospective long-term studies are needed to further define the usefulness of RBC aluminum in diagnosing and following hemodialysis patients with aluminum-induced anemia.

Corticofugal influences of S1 cortex on ventrobasal thalamic neurons in the awake rat

Corticofugal influences on the responses of 39 ventrobasal (VB) thalamic neurons to repetitive stimuli were studied in awake rats by focally suppressing the evoked and spontaneous electrocortical activity of the primary (S1) somatosensory cortex with magnesium or lidocaine plus magnesium. Suppression of the S1 cortex reduced the number of spikes discharged by 19 (66%) of 29 VB units in response to each of 25 electrical stimuli delivered to the medial lemniscus; 9 units were unaffected and 1 showed an increased response to 1-10 Hz stimuli. The responses of 6 (38%) of 16 VB units to electrical somatic stimuli were also reduced following S1 cortical suppression; 9 units were unaffected and 1 showed an increased response to 20-40 Hz stimuli. A comparison of the reduced responsiveness of 5 units studied during medial lemniscal and somatic stimulation did not reveal any additional response attenuation attributable to subthalamic corticofugal influences. We conclude that, in the awake rat, somatosensory transmission to VB thalamic neurons is primarily facilitated by S1 corticothalamic neurons.

Responsiveness of ventrobasal thalamic neurons after suppression of S1 cortex in the anesthetized rat

Corticofugal influences on the responses of ventrobasal (VB) thalamic neurons to repetitive stimuli were studied in anesthetized rats by suppressing primary somatosensory (S1) electrocortical activity with topically applied lidocaine. Effective concentrations of lidocaine were confined to S1 and immediately adjacent cortex and suppressed evoked S1 responses and corticofugal discharges. Suppression of S1 cortex reduced the average number of spikes discharged by 83 VB neurons in response to each of 25 electrical somatic stimuli delivered at frequencies ranging from 1 to 50 Hz. Of 20 units studied both before and after S1 suppression, 14 (70%) showed a similar reduced response to repetitive stimuli. Cortical suppression produced no consistent changes in spontaneous activity, somatic stimulus threshold, response latency, or size of receptive field. There was no significant difference in the effect of cortical suppression on the responsiveness of 8 VB neurons to repetitive medial lemniscal, as compared to somatic, stimuli. We conclude that, in the anesthetized rat, S1 corticofugal activity facilitates somato-sensory transmission to VB neurons and that this facilitation is mediated, at least in part, by corticothalamic neurons.