Radiofrequency catheter ablation for treatment of bundle branch reentrant ventricular tachycardia: results and long-term follow-up

Seven of 120 consecutive patients with inducible sustained ventricular tachycardia (from September 1, 1988 to January 1, 1991) had bundle branch reentrant tachycardia and underwent percutaneous radiofrequency ablation of the right bundle branch. The seven patients had been unsuccessfully treated with a mean of 3 +/- 1 drugs. Four patients presented with syncope and three with aborted sudden death. The baseline electrocardiogram revealed a left bundle branch block pattern in three patients and an intraventricular conduction defect in four. The baseline HV interval was prolonged in each case (79 +/- 2 ms). With use of programmed ventricular extrastimuli, sustained bundle branch reentrant tachycardia was inducible in all patients at a mean cycle length of 283 +/- 17 ms (range 230 to 350). Bundle branch reentrant tachycardia characteristics included atrioventricular dissociation, a His deflection that preceded each QRS complex and spontaneous His to His variation that preceded changes in ventricular tachycardia cycle length. A quadripolar catheter was positioned across the tricuspid valve with the distal electrode tip of the catheter near the right bundle branch. One to three applications of continuous unmodulated radiofrequency current at 300 kHz between the distal electrode and a large posterior skin patch resulted in complete right bundle branch block in all patients, after which none had inducible bundle branch reentrant tachycardia on restudy. On restudy, three of the seven patients had ventricular tachycardia of myocardial origin (not bundle branch reentry). One patient required no therapy; drug or defibrillator therapy was used in the others.(ABSTRACT TRUNCATED AT 250 WORDS)

Patients with supraventricular tachycardia presenting with aborted sudden death: incidence, mechanism and long-term follow-up

A total of 13 (4.5%) of 290 patients with aborted sudden death had either documented (7; 54%) or strong presumptive evidence of supraventricular tachycardia that deteriorated into ventricular fibrillation. Six (46%) of the 13 had an accessory conduction pathway and either atrial fibrillation (5 patients) or paroxysmal atrioventricular (AV) reentrant tachycardia (1 patient) that deteriorated into ventricular fibrillation. Three patients with AV node reentrant tachycardia and four with atrial fibrillation and enhanced AV node conduction presented with supraventricular arrhythmias that deteriorated into ventricular fibrillation. Patients were treated with medical, surgical or catheter ablative procedures designed to prevent recurrences of supraventricular arrhythmias. Four patients received an implanted automatic defibrillator, but none had an appropriate device discharge. Over a follow-up period of 41.6 +/- 33.6 months, 12 patients are alive without symptomatic arrhythmias. One patient died because of severe chronic lung disease and heart failure. Supraventricular tachycardia was the cause of aborted sudden death in approximately 5% of patients referred for evaluation of sudden cardiac death. Treatment directed at prevention of supraventricular tachycardia was associated with an excellent prognosis. Current treatment techniques appear to obviate the need for automatic defibrillator therapy in these patients.

Parkinson's disease in China. Coordinational Group of Neuroepidemiology, PLA

An epidemiological study on the incidence and prevalence of Parkinson's disease (PD) was carried out in 29 provinces, cities and autonomous regions in this country in 1986. The survey was conducted in 117 areas, and 566 patients with PD were found among 3,869,162 persons examined, giving a point prevalence for men and women of 16.9/10(5) and 12.4/10(5), with the highest prevalence after the fifth decade of age. The disease was most prevalent in the southern part of China, especially in Hunan and Guangxi provinces. The incidence was 1.5/10(5)/yr in 1986. Both the prevalence and incidence of PD in China are lower than those in the white race and Japanese.

Influences of Polyactin A on activities of human monocytes in vitro

Effects of Polyactin A (PAA) on abilities of human monocytes to synthesize and secrete interleukin-1 (IL-1) and to modulate natural killer (NK) cell activity in large granular lymphocytes (LGL) were investigated in vitro. Over a wide range of concentrations (0.01-100 micrograms.ml-1), PAA directly induced IL-1 synthesis and secretion, showing the maximal effect at 10 micrograms.ml-1, and evidently synergized with lipopolysaccharides (LPS) of E coli in stimulation of IL-1 production by human monocytes. The manifestation of PAA pretreated autologous monocytes in modulation of NK cell activity was closely related to PAA concentration. A boosting effect of PAA-treated monocytes on NK activity was observed when PAA 10-100 micrograms.ml-1 were used for pretreatment of monocytes, while an inhibitory influence of monocytes was found when PAA 0.01-0.1 microgram.ml-1 were used. These results demonstrate significant effects of PAA on functions of human monocytes, enhancing IL-1 production and affecting their regulative activity on NK cell cytotoxicity.

Comparison of class I- and II-restricted T cell recognition of the identical peptide

There is structural and functional evidence that both class I- and II-restricted T cells recognize short processed peptides bound to MHC molecules. Although the structural conformation of bound peptides remains unknown, no evidence of distinct structural motifs of class I- or class II-restricted peptides has been described. Conversely, two algorithms proposed to predict T cell epitopes, and based on primary amino acid sequence or tertiary structure, are both compatible with many observed class I- and class II-restricted peptides. We previously identified eight class I-restricted peptides which were also recognized by class II-restricted T cells. Based on functional and direct binding studies, additional examples of peptides with both class I and II restrictions have been identified. In this study, we have directly compared the fine specificity of T cell recognition of a single epitope in a single mouse strain in the context of both class I- and class II-restricted responses. Based on a panel of analogue peptides with amino acid substitutions and peptides of various lengths, we observed several striking similarities in the recognition patterns of both class I- and class II-restricted T cells. In addition, some characteristics of recognition were different in the two systems indicating that the recognition processes were similar but not identical.

Pathological study on cerebral amyloid angiopathy

The cerebral amyloid angiopathy (CAA) was pathologically confirmed in 26 cases in which there were 20 cerebral hemorrhages, 2 subarachnoid hemorrhages, 3 cerebral infarctions, and 1 subdural hematoma. The CAA mainly involved the media and extima of small and medium-sized arteries as well as the capillaries of the brain tissue. Half of all cases in our series had the CAA associated vasculopathies (CAA-AV), including microaneurysms, "double barreling", onion skin-like intima, fibrinoid necrosis, clusters of arterioles and perivascular lymphocytic infiltrations. The CAA was often accompanied with the senile plaques and neurofibrillary tangles.

Modified Wicomb's apparatus for preservation of heart for 24 hours

To prolong the time of heart preservation, we modified the Wicomb's perfusion apparatus, in which oxygen flow acts as the source of power and provides oxygenation for the perfused myocardium. Ten adult porcine hearts which had been preserved for 24 hours were resuscitated successfully and continued to beat steadily for more than 1.5-3 hours after reperfusion. Myocardial ultrastructure was observed at the end of preservation and 15-120 minutes after reperfusion. The damages of the myocardial ultrastructure at the end of preservation were reversible.

Characterization of autoreactive T cells. Relative importance of self-peptides versus MHC

The degree to which processed self-peptides contribute to the stimulation of autoreactive T cells has not been determined. In this study we have analyzed a panel of autoreactive T cell hybridomas from normal C57BL/26 mice produced by fusing peripheral lymph node cells with a variant of the BW5147 thymoma line, which does not express endogenous TCR alpha- and beta-chains. All of the autoreactive hybridomas responded to spleen cells expressing the syngeneic I-Ab allele, but not to allogeneic spleen cells. Although all hybridomas were I-Ab restricted, they demonstrated different patterns of reactivity to a panel of APC expressing I-Ab but derived from different genetic backgrounds. In a panel of APC expressing recombinant I-A molecules, changes in the second half of the first domain, which encodes alpha-helix segments that flank the Ag binding site and directly contact the TCR V regions in proposed models, eliminated reactivity of all hybridomas tested. In addition, most of the autoreactive hybridomas also demonstrated inhibition of reactivity to mutations in the amino half of the first domain of the I-A alpha- and beta-chains, which encodes the beta-pleated sheet of the floor of the Ag-binding groove. To confirm the role of processed peptides in the different patterns of reactivity, APC were incubated with competitor Ag and fixed by glutaraldehyde cross-linking before incubation with the autoreactive T hybridomas. The hybridomas were effectively inhibited by exogenous protein and peptide Ag. These results indicate that processed self-peptides are required to activate the autoreactive T cells.

Characterization of autoreactive T cells. Relative importance of self-peptides versus MHC

The degree to which processed self-peptides contribute to the stimulation of autoreactive T cells has not been determined. In this study we have analyzed a panel of autoreactive T cell hybridomas from normal C57BL/26 mice produced by fusing peripheral lymph node cells with a variant of the BW5147 thymoma line, which does not express endogenous TCR alpha- and beta-chains. All of the autoreactive hybridomas responded to spleen cells expressing the syngeneic I-Ab allele, but not to allogeneic spleen cells. Although all hybridomas were I-Ab restricted, they demonstrated different patterns of reactivity to a panel of APC expressing I-Ab but derived from different genetic backgrounds. In a panel of APC expressing recombinant I-A molecules, changes in the second half of the first domain, which encodes alpha-helix segments that flank the Ag binding site and directly contact the TCR V regions in proposed models, eliminated reactivity of all hybridomas tested. In addition, most of the autoreactive hybridomas also demonstrated inhibition of reactivity to mutations in the amino half of the first domain of the I-A alpha- and beta-chains, which encodes the beta-pleated sheet of the floor of the Ag-binding groove. To confirm the role of processed peptides in the different patterns of reactivity, APC were incubated with competitor Ag and fixed by glutaraldehyde cross-linking before incubation with the autoreactive T hybridomas. The hybridomas were effectively inhibited by exogenous protein and peptide Ag. These results indicate that processed self-peptides are required to activate the autoreactive T cells.

Effect of pulsatile reperfusion on myocardial high energy phosphates following global ischemia

To evaluate the effects of pulsatile reperfusion (PR) on the postischemic myocardial phosphometabolites, 17 sheep were put on cardiopulmonary bypass (CPB) and randomly divided into a pulsatile group (P group) and nonpulsatile group (NP group). The heart was arrested by global ischemia for 45 minutes, then defibrillated and reperfused for 2 hours while the circulation was supported by CPB. Myocardial needle biopsies were obtained, and ATP, ADP, and AMP were measured with high performance liquid chromatography. There were no significant differences between the two groups in myocardial ADP and AMP. However, after 120 minutes of reperfusion, the myocardial ATP was restored in the P group, but continued to decrease further in the NP group. Experimental results imply that PR might reduce reperfusion injury and promote recovery of the ischemic myocardium.

Reduction of granulocyte-mediated lung injury in canine cardiopulmonary bypass by anisodamine infusion

The effect of infusing the M-cholinergic receptor blocker anisodamine during cardiopulmonary bypass (CPB) on granulocyte-mediated lung injury was evaluated in sixteen dogs undergoing CPB for 120 min with the aorta crossclamped for 90 min. The treated dogs (n = 8) received a total dose of 15 mg/kg anisodamine hydrochloride before and during CPB whereas the controls (n = 8) received saline only. A significantly reduced sequestration of granulocytes in the lungs was found in the treated dogs as indicated by a lower right-to-left atrium granulocyte gradient 15 minutes after pulmonary recirculation during CPB (p less than 0.05) and less granulocyte accumulation in the lung capillaries after CPB, as shown by histological examination (p less than 0.01). Moreover, oxygen free radical release as indicated by plasma malondialdehyde concentrations was significantly lower (p less than 0.05) in the treated dogs than in the controls towards the end of CPB. Finally, a significantly reduced lung-water content was found 30 min after CPB in the treated dogs as compared with the controls (p less than 0.01). These results suggest that anisodamine administration in this experimental model significantly inhibits pulmonary granulocyte sequestration in CPB and the consequent lung injury induced.

Immunodominance is altered in T cell receptor (beta-chain) transgenic mice without the generation of a hole in the repertoire

Despite the tremendous plasticity of the TCR repertoire, T cells recognize a limited number of antigenic sites (frequently a single site, or immunodominant epitope) on a complex protein Ag. Current models suggest that the immunodominant epitope of a complex protein is the processed peptide that binds to the MHC molecule with the highest affinity. Conversely, the inability of the T cell population to recognize a specific epitope, termed a "hole" in the repertoire, can prevent the immunodominance of a peptide despite efficient processing and MHC binding of the peptide. The role of specific TCR alpha- or beta-chains in determining MHC restriction and recognizing specific epitopes is complex and incompletely understood. To evaluate the contribution of each TCR chain to the functional diversity of the T cell repertoire, we investigated in vivo the T cell response to phage lambda-repressor protein in transgenic mice expressing a single rearranged beta-chain gene (C57L beta mice) in association with the complete germline alpha-chain repertoire. Our results demonstrate that expression of the TCR beta-chain transgene alters the immunodominant epitope recognized by T cells. However, after immunization with the appropriate peptide the transgenic mice can also respond to the nonimmunodominant epitope; thus, the expression of the TCR beta-chain transgene does not create a hole in the repertoire. These data indicate that the primary site, or immunodominant epitope, of an Ag recognized by T cells can be altered by the preimmune TCR repertoire independent of antigen processing and MHC affinity.

Immunodominance is altered in T cell receptor (beta-chain) transgenic mice without the generation of a hole in the repertoire

Despite the tremendous plasticity of the TCR repertoire, T cells recognize a limited number of antigenic sites (frequently a single site, or immunodominant epitope) on a complex protein Ag. Current models suggest that the immunodominant epitope of a complex protein is the processed peptide that binds to the MHC molecule with the highest affinity. Conversely, the inability of the T cell population to recognize a specific epitope, termed a "hole" in the repertoire, can prevent the immunodominance of a peptide despite efficient processing and MHC binding of the peptide. The role of specific TCR alpha- or beta-chains in determining MHC restriction and recognizing specific epitopes is complex and incompletely understood. To evaluate the contribution of each TCR chain to the functional diversity of the T cell repertoire, we investigated in vivo the T cell response to phage lambda-repressor protein in transgenic mice expressing a single rearranged beta-chain gene (C57L beta mice) in association with the complete germline alpha-chain repertoire. Our results demonstrate that expression of the TCR beta-chain transgene alters the immunodominant epitope recognized by T cells. However, after immunization with the appropriate peptide the transgenic mice can also respond to the nonimmunodominant epitope; thus, the expression of the TCR beta-chain transgene does not create a hole in the repertoire. These data indicate that the primary site, or immunodominant epitope, of an Ag recognized by T cells can be altered by the preimmune TCR repertoire independent of antigen processing and MHC affinity.

Membrane oxygenator prevents lung reperfusion injury in canine cardiopulmonary bypass

The effect of blood activation on lung reperfusion injury during cardiopulmonary bypass was investigated in 20 dogs with the use of a bubble oxygenator (n = 10) or a membrane oxygenator (n = 10). In the bubble oxygenator group, significant leukocyte and platelet right to left atrium gradients were found 15 minutes after lung reperfusion (p less than 0.05, p less than 0.01) accompanied by a sharp increase in plasma malondialdehyde concentration 5 minutes after lung reperfusion, whereas no significant right to left atrium gradient of leukocytes or platelets nor significant increase in plasma malondialdehyde concentration was observed in the membrane oxygenator group. In both the bubble oxygenator and membrane oxygenator group, similar mild to moderate lung histological changes were found before lung reperfusion. After lung reperfusion, however, more endothelial cell swelling (p less than 0.05), leukocyte (p less than 0.01) and platelet (p less than 0.01) accumulation in lung capillaries, leakage of erythrocytes into the alveolar space (p less than 0.05), and type I cell damage (p less than 0.05) were found only in the bubble oxygenator group. Eventually, a significantly higher lung water content was found in the bubble oxygenator group than in the membrane oxygenator group (p less than 0.01) after cardiopulmonary bypass. This study indicated that lung injury during cardiopulmonary bypass starts mainly after lung reperfusion, which was correlated with lung leukocyte and platelet sequestration associated with different types of oxygenators.

Abnormal thyroid hormone levels in critical nonthyroidal illness

Low levels of thyroid hormone in the absence of clinical hypothyroidism often happen to patients with critical non-thyroidal illnesses (NTI). Low thyroid hormone concentrations in serum do not necessarily mean hypofunction of the thyroid gland; rather it is a helpful adaptation of the human body to the underlying diseases. We collected 133 hospitalized cases of critical NTI and analyzed the incidence of this phenomenon. Fifty-three per cent of the patients had T3 level lower than 60 ng/dl (normal:85-165 ng/dl) and 60% had T4 level lower than 6 ug/dl (normal:6-12 ug/dl). The lowest levels were observed in patients who had sepsis, were aged over 70 or died in this admission. Free T4 and TSH levels were within normal range in most cases. There is a strong negative correlation between the prognosis and the level of T4 in these patients. Those patients with markedly low levels of T3 and T4 should be treated more sophisticatedly.

Serotonin (5-HT1c) receptors in pig choroid plexus

It is very important to find suitable reaction conditions to attain a high specific binding (specific/total binding) in the receptor binding study. Membrane homogenates of pig choroid plexus are known to have exclusively serotonin (5-hydroxytryptamine, 5-HT) receptor of the subtype 5-HT1c. In this study, we used the membrane preparation of pig choroid plexus tissue and the specific binding of [3H]5-HT was 72-84% to serotonin receptor subtype 5-HT1c, as defined by the inhibition of 1 uM 5-HT, when a radioligand concentration of 0.5 nM of [3H]5-HT was used in the assay. Analysis of the properties of specific [3H]5-HT binding in pig choroid plexus tissue membrane preparation revealed linear Scatchard plots. In Tris-HCl buffer without CaCl2, pargyline or ascorbic acid, high average of affinity dissociation constant (Kd) of 1.3 +/- 0.2 nM (SEM, n = 4) and also a high average of receptor density (Bmax) of 284 +/- 12 fmol/mg of protein were found. Pig choroid plexus proves to be a good material for 5-HT1c receptor binding study.

Influences of a novel immunopotentiator polyactin A on interleukin 1 production and responsiveness in mice

Effects of a novel immunopotentiator Polyactin A (PAA), developed in China, on production and responsiveness of murine interleukin 1(IL-1) were investigated. The results demonstrated that: (1) PAA 0.01-100 micrograms.ml-1 directly induced IL-1 synthesis and secretion from murine peritoneal macrophages (PMO) and markedly enhanced IL-1 production of the mouse PMO stimulated by lipopolysaccharides (LPS) of E coli; (2) IL-1 release from the PMO cultured in PAA 0.1 micrograms.ml-1 was detectable as early as 2 h after the incubation, peaked at 24 h, and then decreased gradually; (3) PAA stimulated and enhanced both IL-1 synthesis and release, but its effect on IL-1 release was stronger; (4) PMO from the mice given po PAA 200 mg.kg-1.d-1 for 7 d produced a higher level of IL-1 than those from control group, and the increase in extracellular IL-1 was more significant than that in intracellular one; (5) in vivo, PAA had no effect on IL-1 receptor expression and IL-1 responsiveness of murine lymphocytes, but eliminated the suppressing effects of cyclophosphamide (Cyc) on IL-1 receptor expression and IL-1 responsiveness of mouse lymphocytes. The above findings provide new explanation for action of PAA and new basis for wider clinical applications of PAA.

Abelson murine leukemia virus transforms preneoplastic Emu-myc transgene-carrying cells of the B-lymphocyte lineage into plasmablastic tumors

E mu-myc transgenic mice were back-crossed to BALB/c mice up to back-cross generation 3. The offspring that included transgene-carrying and -negative mice in approximately equal proportions were randomly divided into 2 groups. Thirty-four mice (group I) were treated with pristane, followed by A-MuLV, and 40 (group II) were injected with A-MuLV alone. Altogether, 16 lymphoid tumors developed in group I and 17 in group II. Nine of the tumors in group I and 4 in group II appeared as ascitic tumors. The ascites contained lymphoblasts and 10 to 45% plasmacytoid cells. These tumors were designated as plasmablastic lymphomas (PLs). All tumors except one were transgene-positive and did not carry translocations. An exceptional tumor in group I carried a variant 6;15 translocation but not the transgene. It obviously corresponds to the regular Abelson + pristane-induced plasmacytoma. Among 11 tested PLs, 10 had a single retroviral insertion site, while one tumor showed 3. Among 18 untreated transgenic descendants (group III), chosen randomly during serial back-crosses, 15 (83%) developed lymphomas, with no sign of plasmacytoid differentiation. The incidence was comparable in all 3 groups, assuming 50% of the mice in groups I and II to be transgenic. The time distribution of tumor development was also similar. Spleen cells from transgene-carrying mice with no clinical sign of lymphoma were infected in vitro with A-MuLV and transplanted i.p. into BALB/c recipients. PLs developed in 26 of 31 pristane-treated recipients, but in only one of 18 untreated recipients. One of 6 PLs tested was monoclonal, whereas the remaining 5 were oligoclonal. They all expressed v-abl. These results show that some of the preneoplastic B-cells that expressed constitutively active myc transgene turned into plasmablasts after infection with A-MuLV. Full development of their neoplastic potential was facilitated by the presence of pristane-granuloma.

[Retinochoroidal changes in experimental severe ocular contusion]

In rabbit models of severe retinal contusion, the retinal edema at the posterior pole resolved in 2 weeks after trauma, leaving central depigmentation and encircling pigmentation. Electroretinogram was diminished permanently and fluorescein angiography showed leakage and staining. The pathologic changes comprised irreversible disruptions of choroidal capillaries, the outer layer of Bruch membrane, retinal pigment epithelium (RPE) and photoreceptor cells, indicating that the regenerative capacity of choroidal capillaries and RPE cells was limited. Transient edema in the inner retinal layers and erythro-phagocytosis by RPE cells were observed.

Preliminary study of the distribution of the toxic elements As, Cd, and Hg in human hair and tissues by RNAA

In order to study the relationships between trace element concentrations of hair and internal body burdens, a radiochemical NAA technique has been used for determination of the elements As, Cd, and Hg in autopsy samples of liver, kidney-cortex, lung, and hair from 24 male persons who died by accident. High significant positive correlations were observed between the As concentration in hair and in kidney-cortex, and between Cd and Zn concentrations in kidney-cortex. The contents of Cd, both for lung and kidney-cortex, were related to the smoking habits of the subjects.

Limitation of myocardial infarct size by a right ventricular assist device

To evaluate the effects of an RVAD on myocardial ischemic injury during right coronary artery (RCA) ligation, a pneumatically driven pusher plate pump was inserted between the right atrium and pulmonary artery, and the RCA was ligated at its origin for two hr. There were 18 sheep, of which nine each served as the control and RVAD groups. Hemodynamic parameters and blood samples were collected from the coronary sinus. Area at risk and area of infarct were detected by gentian violet injection and triphenyltetrazolium (TTC) staining. Hemodynamic parameters (left ventricular systolic pressure (LVSP), cardiac output (CO], and creatine kinase levels in coronary sinus blood tended to be beneficial, to some degree, in the RVAD group. Electron microscopic examination revealed chromatin clumping and mitochondrial destruction, however this ultrastructural damage was more severe in the control group. The ratio of area of infarct to area at risk in the RVAD group was significantly less than that in the control group, being 20.25 +/- 6.93% vs. 47.24 +/- 10.53% (p less than 0.05). The infarct size induced by RCA occlusion was significantly reduced by the RVAD, due to the right ventricular unloading via reduced myocardial oxygen demand.

Morphological and cytogenetic studies of a human synovial sarcoma xenotransplanted into nude mice

Specimens of a synovial sarcoma from the left thigh of a 60-year-old woman and cells from the tumor transplanted into nude mice were examined morphologically and immunohistochemically, and the karyotype was analyzed. Immunohistochemically, cells of both the parent tumor and the transplanted tumor were positive for vimentin and cytokeratin. The multicystic features of the parent tumor were not reproduced in the mice. On ultrastructural examination, the parent tumor cells were found to have dilated channels of endoplasmic reticulum as well as a junctional apparatus, and they formed extracellular spaces. The transplanted tumor cells, in contrast, had a poorly developed endoplasmic reticulum and were devoid of extracellular spaces. Chromosome analysis of the tumor cells revealed a translocation, t (X; 18) (p11; q11), as reported previously for synovial sarcoma, thus suggesting the diagnostic utility of the chromosome pattern for identification of synovial sarcoma.

Intrathecal injection of Iohexol for routine myelography and CT myelography in 1,000 cases

This article is to present the experience in 1,000 cases given intrathecal Iohexol injection during 1985-1988, including conventional myelography in 343 cases, conventional and CT myelography in 572, only CT myelography in 60 and CT cisternography in 25. No convulsions were observed. The frequency of headache was 11.6% and the total uncomfortable subjective reaction was 19.6% after intrathecal injection, but no serious complications were found. Because of very low frequency of side effects after this injection, most of the examinations can be made in the outpatient departments. In our clinical experience, Iohexol appears to be a myelographic contrast medium with diagnostic capabilities and less morbidity compared to Metrizamide. Thus Iohexol seems to be well suited for intrathecal injection and will replace metrizamide in this respect.

Characterization of a major DNA-binding domain in the herpes simplex virus type 1 DNA-binding protein (ICP8)

We have studied the major DNA-binding protein (ICP8) from herpes simplex virus type 1 to identify its DNA-binding site. Since we obtained our protein from a cell line carrying multiple chromosomally located copies of the ICP8 gene, we first analyzed this protein to assess its similarity to the corresponding viral protein. Our protein resembled the viral protein by molecular weight, response to antibody, preference for binding single-stranded DNA, and ability to lower the melting temperature of poly(dA-dT). To define the DNA-binding domain, we subjected the protein to limited trypsin digestion and separated the peptide products on a sodium dodecyl sulfate-polyacrylamide gel. These fragments were then transferred to a nitrocellulose membrane, renatured in situ, and tested for their ability to bind DNA. From this assay, we identified four fragments which both bound DNA and exhibited the expected binding preference for single-stranded DNA. The sequence of the smallest of these fragments was determined and corresponds to a polypeptide spanning residues 300 to 849 in the intact protein. This peptide contains several regions which may be important for DNA binding based on sequence similarities in single-stranded DNA-binding proteins from other herpesviruses and, in one case, on a conserved sequence found in more distant procaryotic and eucaryotic proteins.