Vasorelaxing effect in rat thoracic aorta caused by fraxinellone and dictamine isolated from the Chinese herb Dictamnus dasycarpus Turcz: comparison with cromakalim and Ca2+ channel blockers

The components of Dictamnus dasycarpus Turcz were tested for their vasorelaxing effect on the rat aorta, and fraxinellone and dictamine were shown to be effective vasorelaxants. In high K+ (60 mmol/l) medium, Ca2+ (0.03 to 3 mmol/l)-induced vasoconstriction was inhibited concentration-dependently by both agents. The IC50 for fraxinellone and dictamine were calculated to be about 25 mumol/l and 15 mumol/l (for Ca2+ concentration of 1 mmol/l), respectively. Cromakalim (0.2-10 mumol/l) relaxed aortic rings precontracted with 15 but not 60 mmol/l of K+. Fraxinellone and verapamil were more potent and effective in producing relaxation in 60 mmol/l than in 15 mmol/l K(+)-induced contraction. However, dictamine was more potent in producing relaxation in 15 mmol/l K(+)-induced contraction. Nifedipine (1 mumol/l), dictamine (100 mumol/l) and fraxinellone (100 mumol/l) relaxed the aortic contraction caused by KCl or Bay K 8644. The tonic contraction elicited by noradrenaline (NA, 3 mumol/l) was also relaxed by dictamine (500 mumol/l), but not by fraxinellone (500 mumol/l) in the nifedipine (1 mumol/l)-treated aorta. This relaxing effect of dictamine persisted in endothelium-denuded aorta. Glibenclamide (10 mumol/l) shifted the concentration-relaxation curve of cromakalim, but not that of dictamine, to the right in rat aortic rings precontracted with NA. Dictamine (500 mumol/l) did not affect tonic contraction of NA which are reduced by H-7 (1 mumol/l) in Ca(2+)-depleted medium. In conclusion, fraxinellone is a selective blocker of voltage-dependent Ca2+ channel, while dictamine relaxed the rat aorta by suppressing the Ca2+ influx through both voltage-dependent and receptor-operated Ca2+ channels.

[IL-2 potentiates the IL-3 production by ConA activated mouse splenic T cells]

In addition to the regulation of T cell growth, IL-2 exerts effects on the induction of certain lymphokines. We show here that IL-2 synergizes with 5 micrograms/ml of ConA to promote the production of IL-3 in mouse splenic T cell cultures. IL-3 was measured as CFU-GEMM-inducing activity on mouse bone marrow progenitor cells in the supernatant of the stimulated mouse splenic T cells (TCM). The resting T cells produced no CFU-GEMM-inducing activity, but could be induced to produce low level of CFU-GEMM-inducing activity in the presence of ConA. In vitro exposure to IL-2 markedly increased CFU-GEMM-inducing activity production (nearly up to 8-fold) by the ConA-activated T cells. Optimal stimulation was observed when 80 u/ml IL-2 was used for 48 h incubation. Anti-mouse IL-3 monoclonal antibody inhibited the CFU-GEMM inducing activity of TCM. Moreover, the TCM stimulated the proliferation of IL-3 dependent cell line FDC-P1. We also show that IL-2 and ConA-treated T cells expressed high level of IL-3 mRNA through dot blot analysis. These results confirmed the nature of CFU-GEMM-inducing activity of TCM as IL-3. The capacity of IL-2 to promote the production of IL-3 may represent an important mechanism by which it mediate the communication between the immune and hematopoietic systems.

Determination of trace iodine in food and biological samples by cathodic stripping voltammetry

This paper describes a sensitive and selective method for the determination of iodine in food and biological samples. The method involves treatment of samples by combustion in an oxygen flask and determination of iodide by cathodic stripping voltammetry of the solid phase formed with the quaternary ammonium salt Zephiramine as the ionic associating agent; Br- is used as the complexing agent in the preconcentration process. We have studied the effect of concentration of Zephiramine, Br-, I-, and some other elements presented, deposition potential, preelectrolysis time, and scan rate, on the stripping curve shape and maximum stripping current. Determinations of trace iodine in table salt, laver, and eggs were demonstrated as practical examples.

RFLP-based genetic map of rye (Secale cereale L.) chromosome 1R

A map of chromosome 1R of rye was constructed using 16 molecular and biochemical loci. From long arm to short arm, known-function loci were placed in the order: XAdh - XLee - Glu-R1[Sec-3] - XPpdk-1R - XEm-1R-1 - XEm-1R-2 - Centromere - XNor-R1 -Gpi-R1 - XGli-R1 [Sec-1a] along with six anonymous genomic and cDNA clones from wheat. The map, which spans 106 cM with 12 loci clustered in a 15-cM region around the centromere, shows reasonably good agreement with previously published maps for the centromeric region, whereas the XNor-R1 - Gpi-R1 region gives a much larger distance than previously reported.

Influenza virus RNA in the lung and lymphoid tissue of immunologically intact and CD4-depleted mice

The distribution and clearance of viral RNA (vRNA) and mRNA has been analysed for the acute and recovery stages of the pneumonia induced by intranasal infection of C57BL/6J mice with H3N2 influenza A viruses. Amplification of viral genomic material by the polymerase chain reaction showed that the influenza haemagglutinin (HA) gene was eliminated from the lungs of immunologically intact mice by day 14 post-infection, whereas in vitro depletion of the CD4+ T cells delayed clearance by at most 4 days. Viral RNA encoding the HA gene was first demonstrated in the regional mediastinal lymph nodes at 48 h, and continued to be present until day 6 or day 10 after infection of the intact and CD4-depleted mice, respectively. Evidence for the presence of vRNA in the thymus, but not in the mesenteric lymph nodes or the spleen, was found in some situations. Otherwise, the distribution and clearance of vRNA was as would be predicted from earlier studies using virus isolation procedures to monitor localization patterns, and shows a lack of long-term persistence of the influenza virus genome.

31P magnetic resonance spectroscopy (MRS) of experimental orbital myositis

We described a model of orbital myositis that was induced by 12-0-tetradecanoyl-phorbol-13-acetate (TPA) injection into the superior rectus muscle of New Zealand white rabbits. In this study, in vivo 31P magnetic resonance spectroscopy (MRS) was performed with a 4.7 Tesla Oxford (Oxford Instruments, Oxford, England) magnet to monitor the evolution of muscle inflammation in control animals and the response of this model to external beam radiation. 31P MRS showed a dramatic increase in high-energy phosphorus and phospholipid metabolites 48 hr after TPA injection. These spectra were similar to those from implanted allogenic fibroblasts. Within 18-48 hr after a single dose (400 cGy) or sequential doses (3 days at 400 cGy) of orbital irradiation, reduced extraocular muscle swelling and a significant decrease of all 31P metabolites occurred. A decrease (63 +/- 6%) in the signal-to-noise (S/N) ratio of the control inflamed muscle 31P MR spectra increased by 28 days after inflammation. Two days after single-dose radiation, 31P MR metabolites were significantly lower (58 +/- 5%, P less than 0.012) than control spectra. These postradiation spectra mirror the 28-day control spectra and are consistent with previous histologic data that show decreased fibroblastic activity. Change in 31P MRS was a sensitive indicator of treatment response latency.

[A random sample study of therapeutic effect of beta-receptor blocking agents in patients with subarachnoid hemorrhage]

The Study on the treatment of 50 cases of subarachnoid hemorrhage (by applying beta-receptor blocking drug propranolol) and the control group of 55 cases revealed that the mortalities of the therapeutic group and the control group were respectively 4% and 9.2% (P less than 0.05) the incidences of the cerebral vasospasm were 2% and 10.6% (P less than 0.01) and those of the abnormal electrocardiograms were 6% and 21.8% (P less than 0.01). The differences between the two group were significant. The function of propranolol may be associated with the sudden increase of catecholamine after subarachnoid haemorrhage and there for the drug has the function of protection of the cardiac muscle and prevention of the cerebral vasospasm.

A clinical pregnancy after a simple method of zona cutting, cryopreservation, and zygote intrafallopian transfer

A 30-year-old nulliparous woman, who was infertile for greater than 3 years, conceived after the procedures of a simple method of zona cutting, cryopreservation, and ZIFT. This case illustrates: (1) acid medium, chymotrypsin, or sucrose are not needed for the procedure of zona cutting; (2) the zygotes resulting from zona cutting survive through freezing and thawing; and (3) oocyte retrieval can be done concomitant with conservative surgery for endometriosis.

Cerebral cysticercosis

We studied 143 cases of cerebral cysticercosis over a 30-year period. In 46 there was hydrocephalus due to cysts obstructing the cerebrospinal fluid pathways, with signs of hydrocephalus and cerebellar dysfunction. In 97 there were cysts in the cerebral parenchyma, causing symptoms of intracranial hypertension alone in 22 cases, with additional neurological deficits in the remainder. Before 1980 diagnosis was made by pneumoencephalography and ventriculography, but since then it has mostly been done by computed tomography. In 28 cases scanned, typical abnormalities were present in 25. Complement fixation tests were positive in serum in 74% of cases and in cerebrospinal fluid in 73%, and the enzyme-linked immunosorbent assay test was positive in serum in 90% and in cerebrospinal fluid in 92%. Treatment of cases with hydrocephalus was by removal of the cysts at craniotomy, with placement of a shunt where necessary. Intracranial hypertension caused by parenchymal cysts was treated with steroids and osmotic agents, if possible. In resistant cases subtemporal decompression was needed, unilateral in 55 cases and bilateral in eight. Mortality in the acute stage was 11%, with a further 20% at follow up.

[Comprehensive study of percutaneous transhepatic aspiration bile culture and cholangiography]

In this study, the results of transhepatically aspirated bile culture, and cholangiography done in 220 cases with biliary tract diseases were presented. Aerobes and anaerobes were found in 76.4% and 64.7% of all samples respectively. Patients with partial common bile duct obstruction from stricture and choledocholithiasis had markedly higher positive cultures than that with simple gallbladder stones and complete common duct obstruction secondary to carcinomas of the pancreas or ampulla. Bile culture from patients with symptomatic cholangitis was much more often positive than those with asymptomatic cholangitis. It was also found that patients with positive bile cultures were more prone to after-PTC acute cholangitis. This study suggested that bile organisms are mainly from the gut, bile organisms and bile duct obstruction are two major causes of acute cholangitis, abrupt elevation of bile pressure during PTC procedure was also a causing factor of acute cholangitis. The authors advocate the comprehensive and prophylactic use of antibiotics both effective to aerobes and anaerobes in the treatment of biliary tract infection.

Coding properties of the S and the M genome segments of Sapporo rat virus: comparison to other causative agents of hemorrhagic fever with renal syndrome

Three serologically distinct groups of hantaviruses have been associated with severe, moderate, and mild forms of hemorrhagic fever with renal syndrome (HFRS). To gain a better understanding of the genetic variation among these viruses, we cloned and sequenced the M and the S genome segments of Sapporo rat virus, an etiologic agent of moderate HFRS, and compared the predicted gene products to those of Hantaan virus, and the Hällnäs strain of Puumala virus, which are etiologic agents of severe and mild HFRS, respectively. The SR-11 S segment consisted of 1769 nucleotides and had an open reading frame (ORF) in the virus-complementary sense RNA with a coding capacity of 429 amino acids. Deduced amino acids from the SR-11 S segment ORF displayed 83% homology with those of Hantaan nucleocapsid (N) protein. Comparison of the S segment ORFs of all three viruses revealed 58% homology. No evidence for additional nonstructural protein(s) encoded by the SR-11 S segment was obtained. The SR-11 M segment consisted of 3651 nucleotides and had an ORF in the virus-complementary sense RNA with a coding capacity of 1134 amino acids. Amino acid sequences predicted from the SR-11 M segment ORF were 75% homologous with those encoding Hantaan G1 and G2 envelope glycoproteins. Comparison of the deduced amino acid sequences of the M segment ORFs of SR-11, Hantaan, and Hällnäs viruses revealed a 43% homology for amino acids constituting the G1 proteins and a 55% homology for amino acids constituting the G2 proteins of the three viruses. The envelope proteins of SR-11 virus were localized within the M segment ORF by amino-terminal sequence analysis of purified G1 and G2. G1 initiated at amino acid 17 and G2 at amino acid 647 within the ORF. Five potential asparagine-linked glycosylation sites were identified in the SR-11 G1 coding sequences, four of which were conserved between Hantaan and SR-11 viruses and three of which were conserved among all three viruses. One potential glycosylation site was identified in the SR-11 G2 coding sequences and was conserved among Hantaan, SR-11 and Hällnäs viruses. Cysteine residues were highly conserved within the M segment ORFs of all three viruses, suggesting a similar structure and function of the G1 and G2 proteins.

In vitro fertilization, gamete intrafallopian transfer and combined IVF-GIFT results: three-year experience at Chang Gung Memorial Hospital

A review is presented summarizing the IVF-ET, GIFT and combined IVF-ET-GIFT experienced at Chang Gung Memorial Hospital. Since the building of an aseptic dust free laboratory next to the operation room, the clinical pregnancy rate has been 12.2% per embryo transfer in IVF-ET, 16.7% in the GIFT program and 30.0% in the combined IVF-GIFT program. The overall clinical pregnancy rate was 14.9%. The overall pregnancy rate appeared to be independent of the causes of infertility, be it tubal factor, endometriosis or unexplained infertility. It was lower in couples with male factor or combined factors. The different regimens for follicular stimulation were hMG-hCG, clomiphene-hMG-hCG and FSH-hMG-hCG. No one regimen showed a better pregnancy rate than the others. The methods of oocyte retrieval were laparascopy, laparotomy, transbladder ultrasound-guided, and transvaginal ultrasound-guided retrieval. There were 4.53 oocytes retrieved pertreatment cycle. The transvaginal ultrasoundguided oocyte retrieval has greatly simplified the procedures in the IVF-ET program. The patient selection was important not only for the indications but also for the methods of IVF-ET, GIET and combined IVF-GIFT.

Extensive heterogeneity in the hemagglutinin of egg-grown influenza viruses from different patients

We establish that the cultivation of influenza (H3N2) virus from any infected individual in chicken embryos (eggs) can result in the isolation of viruses with antigenic and/or structural heterogeneity in the hemagglutinin (HA) molecule. This variability contrasted sharply with the apparent lack of antigenic alterations in the HA of influenza viruses isolated from patients in Madin Darby canine kidney (MDCK) cells. The most common subpopulation of egg-grown influenza viruses had the same phenotype as MDCK cell-grown virus and may best represent the virus circulating in humans. It should be considered the optimal strain for use in vaccine and epidemiologic studies.

Rhythms of serum melatonin in patients with spinal lesions at the cervical, thoracic or lumbar region

The neural pathway essential for the diurnal rhythm of serum melatonin was studied in humans. Blood samples from 17 patients with chronic lesions of cervical (n = 8), low thoracic or lumbar (n = 9) spinal cord were collected at 0200, 0400, 1000 and 1400 h of their normal light-dark cycle. Blood samples were also collected from eight control subjects at 0200 and 1400 h. No special treatment of food, drug or photoperiod was implemented. Serum melatonin was extracted by dichloromethane and determined by radioimmunoassay. In patients with cervical spinal lesions (C3-C7), it was found that serum melatonin levels were low and no diurnal rhythm was observed. Conversely, diurnal rhythm of circulating melatonin with significantly higher levels (P less than 0.01) in the dark period were observed in individuals with injuries at the low thoracic or lumbar regions (T9-L2). In the second experiment, blood samples from two other patients were collected for three consecutive days during acute period of spinal injuries (cervical or upper thoracic region) and serum melatonin concentrations were determined. Again, there were low levels of serum melatonin with no observable diurnal rhythm in the patient with cervical lesion (C4-5). However, diurnal rhythms were maintained with high levels in the dark period in the patient with upper thoracic spinal (T2-3) transection. Our data suggest that the cervical region of the spinal cord is part of the neural pathway essential for the diurnal rhythm of pineal melatonin secretion in human beings.

Chemodectoma of the temporal bone: a comparison of surgical and radiotherapeutic results

Between January 1950 and December 1981, 32 patients with chemodectomas of the temporal bone were treated at the University of Iowa Hospitals and Clinics. Thirteen patients were treated with surgery alone, 15 with radiation therapy alone, one with preoperative radiation therapy and surgery, and three with surgery and postoperative radiation therapy. In general, the patients treated with radiotherapy alone or combined therapy (radiotherapy group) had more advanced tumors than those treated with surgery alone (surgery group). For the surgery group, the initial local control rate was 46% and the ultimate local control rate 84% following salvage with additional surgery, 31% developed complications, and 78% survived 10 years. For the radiotherapy group, 84% had local tumor control, 11% developed complications, and 77% survived 10 years. These results demonstrate that radiation therapy is an effective treatment modality for chemodectomas of the temporal bone.

Inoperable adenocarcinoma of endometrium: radiation therapy

Between 1960 and 1979, 41 patients with adenocarcinoma of the endometrium who were poor surgical risks were treated with radiation therapy at the University of Iowa. Local tumor control was achieved in 78% of the patients, 5% manifested complications, and 46% survived 5 years ("uncorrected" 5-year survival rate). Intercurrent disease was the major cause of death (54%), and intrauterine recurrence (22%) was the most frequent recurrence. Intraperitoneal spread (12%) occurred as commonly as hematogenous metastases (12%). Three of nine local failures occurred after 5 years. Local control rates correlated well with clinical stage, and the survival rates correlated well with the stage and grade of the tumor. Local tumor control was achieved in 95% of patients who received greater than 7,000 mg-h intracavitary radium, compared with 63% of patients treated with less than 7,000 mg-h.

Production of IgA monoclonal antibodies against influenza A virus

Nineteen IgA monoclonal antibodies against influenza A virus X-31 were obtained following intranasal infection of mice with influenza A virus X-31. It was demonstrated that specificities of IgA monoclonal antibodies are similar to those of IgG monoclonal antibodies. These IgA antibodies might be useful for the study of mucosal immunity against influenza A viruses. Infection may be an easier and better way of producing monoclonal antibodies against some viral agents.

The use of micropeptide maps and monoclonal antibodies for antigenic variation analysis of influenza A viruses isolated in China from 1972 to 1983

125I-labelled haemagglutinin (HA) micropeptide mapping and haemagglutinin inhibition (HAI) tests with monoclonal antibodies were used in analysing antigenic variation of six strains of influenza A virus isolated from 1972 to 1983 in China. The results from micropeptide mapping generally coincided with those of sequence analysis. 125I-labelled HA micropeptide mapping is a simple, reproducible and practical method for surveillance of influenza, especially in combination with HAI test using monoclonal antibodies.

Comparative analyses of the specificities of anti-influenza hemagglutinin antibodies in human sera

Estimates of the variety of specificities of anti-influenza hemagglutinin antibodies in postinfection human sera taken between 1969 and 1971 and in 1978 were made by using Fab fragments of defined monoclonal antibodies in competitive virus-binding assays. The results obtained with the sera taken between 1969 and 1971 indicated that different sera contained antibodies with different ranges of specificities, whereas the 1978 sera mainly contained a broad range of antibodies. The results are discussed in relation to the mechanism of antigenic drift in influenza virus, the commonly observed antigenic heterogeneity of influenza virus isolates, and the efficacy of antiinfluenza vaccination.

Fusion mutants of the influenza virus hemagglutinin glycoprotein

The influenza virus hemagglutinin (HA) mediates viral entry into cells by a low pH induced membrane-fusion event in endosomal vesicles. Mutant viruses with altered pH dependence for both hemolysis and the HA conformational change required for fusion were selected for their ability to grow in cells treated with amantadine hydrochloride, which raises the endosomal pH. The amino acid sequence and three-dimensional location of 19 substitutions on the HA are reported. The mutations fall into two groups, one that results in the destabilization of the pH 7.0 location of the hydrophobic N-terminal HA2 peptide, and a second that results in the alteration of intersubunit contacts, suggesting a large distortion or disruption of these contacts in the "fusion-active" conformation.

Studies on the adaptation of influenza viruses to MDCK cells

The amino acid sequences and biological properties of the haemagglutinin of three variants of the influenza virus X-31 (H3N2) selected for their capacity to grow in MDCK cells are reported. In two variants, amino acid substitutions at HA1 residues 8 and 144 correlated with the loss of a site for glycosylation and specific changes in antigenicity, respectively. In all three variants substitution of an arginine residue for histidine at HA1 position 17 was correlated with increased pH optima of haemolysis. The importance of this substitution for cleavage of the haemagglutinin precursor required to produce infectious virus is discussed in relation to the three-dimensional structure of X-31 haemagglutinin.

Habituation of human limbic neuronal response to sensory stimulation

Hippocampal, parahippocampal gyrus, and amygdalar neuronal responses to visual and acoustic stimuli were analyzed during trains of several hundred stimulus repetitions as part of an investigation of sensory pathways to medial temporal lobe structures in complex-partial epilepsy patients who were being monitored with depth electrodes. Ten percent of more than 500 single and multiple units tested were responsive to simple sensory stimuli. The majority of the responsive units were recorded in the posterior parahippocampal gyrus (HG) during visual stimulation. Although neurons in pes hippocampi (PH; Ammons's horn) were also responsive to photic stimuli, no visually responsive units were found in amygdala. Very few units were responsive to acoustic stimuli, and these were found only in PH and amygdala, and not in HG. Significant trends of increase or decrease in response amplitude during trains of stimuli were found in all acoustically responsive units. Significant trends of visual response amplitude increase or decrease were found in 20% of PH units, and in 44% of HG units. Mean latencies of acoustically responsive units were longer than those of visually responsive units, and latencies of PH sensory units showing decremental response were longer than nondecremental PH units. Rate of response decrement was usually linear for acoustic responses and exponential for visual responses. The response dynamics of medial temporal lobe neurons are compared with those described in the animal limbic system and are related to habituation of human sensory evoked scalp potentials.

Polymerization of vector DNA after transfection into hamster fibroblast cells

We have transformed hamsters lung fibroblasts with two cloned, selectable markers, the widely used pSV2gpt vector and pNEO3, which confers resistance to neomycin. Analysis of DNA extracted from both individual and pooled groups of several hundred transformants reveal that in these carrier DNA-free transformation experiments, the vector DNA are found in concatenate forms in the transformants. The copy number of the integrated vectors can vary from a few to several hundred. In addition, the efficiency of transformation is ten times higher in the case of pSV2gpt.

The role of RNA primer in discontinuous DNA replication in isolated nuclei from HeLa cells

RNA-primed discontinuous DNA synthesis was studied in an in vitro system consisting of washed nuclei from synchronized S-phase HeLa cells. A new technique proved useful for the purification of short nascent fragments of DNA (Okazaki fragments). Mercurated dCTP was substituted for dCTP in the DNA synthesis reaction. Short nascent pieces (4-6 S) of mercurated DNA were found to bind preferentially to sulfhydryl-agarose, and could be eluted with mercaptoethanol. The isolated fragments were assayed for the presence of covalently linked RNA by the spleen exonuclease method described by Kurosawa et al. (Kurosawa, Y., Ogawa T., Hirose, S., Okazaki, T. and Okazaki, R. (1975) J. Mol. Biol. 96, 653-664). Following a 30 s incubation with [3H]TTP in the absence of added ribonucleotides, approximately 20% of the nascent strands synthesized in washed nuclear preparations had RNA attached. These RNA primers either preexisted in the nuclei or were formed from endogenous ribonucleotides. The 5' ends of the primers appeared to be largely in a phosphorylated state. In the absence of added ribonucleotides, these RNA-DNA linkages disappeared with 2 min, whereas if ribonucleotides were added, the number of RNA primers increased to 40% and remained at this level for greater than 2 min. To obtain maximal levels of RNA primer, the addition of all three of the ribonucleotides, rCTP, rGTP, rUTP (0.1mM), as well as high levels of rATP (5mM) was required. Addition of ribonucleotides also markedly enhanced the amount of nascent DNA fragments synthesized. However, in the absence of added ribonucleotides, after RNA primers had disappeared, nascent DNA fragments were still initiated at a significant rate. These results suggest that RNA primers play an important role in the initiation of Okazaki fragments but that synthesis can also be initiated by alternative mechanisms. An important role for ATP in RNA primer synthesis is suggested.

Evidence for the absence of DNA proofreading in HeLa cell nuclei

[3H]2-Aminopurine deoxyribonucleoside triphosphate and [32P]dATP were added exogenously at equimolar concentrations to washed HeLa cell nuclei both in the presence and absence of cell cytoplasm. The observed ratio of 2-aminopurine/adenine deoxyribonucleotide incorporation into DNA was about 12%, which is consistent with 2-aminopurine misinsertion frequencies measured in cell-free assays, for various DNA polymerases including alpha-polymerase from calf thymus, Escherichia coli polymerase I, and several mutant and wild type bacteriophage T4 polymerases. Based on the 12% 2-aminopurine/adenine misincorporation ratio, we propose that proofreading of replicating DNA is not occurring in HeLa nuclei, and that discrimination against 2-aminopurine incorporation is governed primarily by a 1.1 kcal/mol difference in free energy between 2-aminopurine.thymine and adenine.thymine base pairs rather than by properties attributable to either the mammalian DNA polymerase or HeLa cell nuclear replication apparatus.

The stomach as a site for rapid nutrient reinforcement sensors

Rats with inflated cuffs placed around the pyloric sphincter were given a choice between two nonnutritive solutions. Ingestion of one solution was paired with nutritive intragastric injections and ingestion of the other was paired with saline injections. The preference of rats for the nutrient-paired flavors indicates that the stomach alone can rapidly detect the arrival of nutritive substances.

Histidinemia produced in the rat by treatment with nitromethane1

Metabolic effects of in vivo administration of nitromethane, a histidase inhibitor, were studied in the rat. Histidinemia produced by feeding a 5-percent histidine diet to the rat was included for comparison. Rats injected subcutaneously with nitromethane every other day appeared to be histidinemic, with a plasma histidine level of 43 mumol/100 ml (control 9.2 mumol/100 ml) after 12 days of treatment. Histidine concentrations in the brain, liver, kidney, and urine of the nitromethane-treated rats were also increased. Liver histidase activity was decreased about 78 percent after nitromethane administration, and the rate of in vivo CO2 production from histidine was also depressed. No abnormal change in liver and kidney sizes was observed in these animals. Rats fed the 5-percent histidine diet showed markedly higher plasma histidine concentrations (99 mumul/100 ml) than the nitromethane-treated rats. The magnitude of increase in plasma histidine in the histidine-fed rats was considerably greater than that observed in humans with histidinemia. Furthermore, the liver histidase activity was decreased only by about 20 percent, and a significant increase in liver and kidney sizes was noted in the histidine-fed animals. These findings indicate that histidinemia produced by nitromethane administration is a better model for studies of the genetic disorder than histidinemia induced by high levels of histidine in the diet.