Effects of the par locus on the growth rate and structural stability of recombinant cells

A decreased growth rate of recombinant cells is observed when a cloned gene protein encoded in a multicopy plasmid is induced from a strong promoter. This negative effect on the cell growth rate may be the consequence of alternate use or reallocation of energy, precursor metabolites, and protein synthesizing machinery. In order to analyze the causes for this adverse effect, we have studied how genetic elements present in multicopy plasmids affect the growth of recombinant Escherichia coli (K12 delta H1 delta trpEA). Turning on of the PL promoter, whether or not protein-coding sequences were present downstream of the promoter, decreased the growth of the recombinant cells by 15-50%. This result suggests that the essential factor(s) for cell growth may be sequestered by the genetic elements present in the plasmids and thus may cause the decreased growth. The negative effect of the de-repressed PL promoters on cell growth was partially reversed when the par sequence from pSC101 was inserted into the same plasmid. In each case when the plasmid carried only the PL promoter, the PL promoter followed by the N-terminal part of the protein-coding region, or the PL promoter followed by complete sequences encoding a protein, the par sequence exhibited a positive effect on the growth rate of the recombinant cells, which usually grow at a slower rate than the host cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Gender differences in the individual characteristics and life contexts of late-middle-aged and older problem drinkers

This study focuses on gender differences in the individual characteristics and life contexts of late-life problem drinkers. Late-middle-aged women with drinking problems (n = 183) consumed less alcohol, had fewer drinking problems, and reported more recent onset of drinking problems than did their male counterparts (n = 476). They also used more psychoactive medications, were more depressed, and were less likely to seek alcohol treatment. Consistent with a gender role perspective on alcohol abuse, problem-drinking women had more family-related and fewer financial stressors than did problem-drinking men. Contrary to expectation, however, problem-drinking women reported more support from children, extended family members, and friends than did problem-drinking men. Moreover, women who continued to have drinking problems over a 1-year interval reported some unexpected short-term benefits at follow-up, including reduced spouse stressors. Women who had remitted at follow-up experienced less spouse support, and more family-related stressors and depression than did remitted men. They also lost support from extended family members over the 1-year interval. The results suggest a need for screening and treatment efforts tailored more closely to the life circumstances of women with late-life drinking problems.

Intestinal infarction secondary to mesenteric venous thrombosis: CT-pathologic correlation

We reviewed CT of four patients with surgically proved bowel infarction secondary to superior mesenteric vein (SMV) thrombosis. Pathologic correlation was available in all patients. Three patients had thrombus in both portal vein and proximal SMV and the remaining patient had thrombus that was seen only in the peripheral branches of the SMV. Contrast-enhanced CT showed a segmental distribution of marked concentric bowel wall thickening in all four patients. Two patients also showed zones of different attenuation in the bowel wall, which were caused by varying degrees of edema and hemorrhage in the submucosa. Dense peripheral enhancement of the bowel wall was present in one patient. Other CT findings included ascites and mesenteric changes such as edema and vascular engorgement. The combination of thrombus in the SMV with bowel wall thickening strongly suggests bowel infarction and, therefore, warrants initiation of appropriate therapy.

Replication of type 1 human immunodeficiency viruses containing linker substitution mutations in the -201 to -130 region of the long terminal repeat

In previous transfection analyses using the chloramphenicol acetyltransferase reporter gene system, we determined that linker substitution (LS) mutations between -201 and -130 (relative to the transcription start site) of the human immunodeficiency virus type 1 long terminal repeat (LTR) caused moderate decreases in LTR transcriptional activity in a T-cell line (S. L. Zeichner, J. Y. H. Kim, and J. C. Alwine, J. Virol. 65:2436-2444, 1991). In order to confirm the significance of this region in the context of viral replication, we constructed several of these LS mutations (-201 to -184, -183 to -166, -165 to -148, and -148 to -130) in proviruses and prepared viral stocks by cocultivation of transfected RD cells with CEMx174 cells. In addition, two mutations between -93 and -76 and between -75 and -58 were utilized, since they affect the nuclear factor kappa B (NF-kappa B)- and Sp1-binding sites and were expected to diminish viral replication. Our results suggest that while transfection analyses offer an adequate approximation of the effects of the LS mutations, the analysis of viral replication using a mutant viral stock presents a more accurate picture, which is sometimes at variance with the transfection results. Three mutants (-201/-184 NXS, -165/-148 NXS, and -147/-130 NXS) had effects on viral replication that were much more severe than the effects predicted from their performance in transfection analyses, and the effects of two LS mutations (-201/-184 NXS and -183/-166 NXS) were not predicted by their effects in transfection. In addition, we observed cell type-specific permissiveness to replication of some mutant viruses. In the cell types tested, the LS mutations indicated an apparent requirement not only for the intact NF-kappa B and SP1-binding sites but also for several regions between -201 and -130 not previously associated with viral infectivity.

Effects of beta 6 amino acid hydrophobicity on stability and solubility of hemoglobin tetramers

The relationship between different amino acids at the beta 6 position of hemoglobin and tetramer stability was addressed by a site-directed mutagenesis approach. Precipitation rates during mechanical agitation of oxyhemoglobins with Gln, Ala, Val, Leu and Trp at the beta 6 position increased 2, 5, 13, 21 and 53 times, respectively, compared with that for Hb A. There was a linear relationship between the log of the precipitation rate constant and amino acid hydrophobicity at the beta 6 position, suggesting that enhanced precipitation of oxy Hb S during mechanical agitation results in part from increased hydrophobicity of beta 6 Val. Deoxyhemoglobin solubility increased in the order of beta 6 Ile, Leu, Val, Trp, Gln, Ala and Glu suggesting that hydrophobic interactions between beta 6 Val and the acceptor site of another hemoglobin molecule during deoxy-Hb S polymerization not only depend on hydrophobicity but also on stereospecificity of the amino acid side chain at the beta 6 position. Furthermore, our results indicate that hydrophobic amino acids at the beta 6 position which promote tetramer instability in the oxy form do not necessarily promote polymerization in the deoxy form.

The role of state-trait anxiety in insomnia and daytime restedness

This study examined the relationships among anxiety, nocturnal sleep, and daytime restedness over a 1-week period, using the Spielberger State-Trait Anxiety Inventory and daily sleep logs. Among both insomniacs and controls, between-subjects correlations showed a significant negative relationship between state anxiety at bedtime and restedness during the day. Neither variable was related to nocturnal sleep variables. Within-subject correlations showed similar relationships between state anxiety and restedness the following day. For insomniacs, but not for normal sleepers, bedtime state anxiety was also significantly correlated with sleep latency. The authors hypothesize that anxiety, not sleep deprivation, may be responsible for the insomniac's complaint of daytime fatigue.

Rapid and sensitive method for detection of Shiga-like toxin-producing Escherichia coli in ground beef using the polymerase chain reaction

A rapid and sensitive method for detection of Shiga-like toxin (SLT)-producing Escherichia coli (SLT-EC) with the polymerase chain reaction (PCR) is described. Two pairs of oligonucleotide primers homologous to SLTI and SLTII genes, respectively, were used in multiplex PCR assays. The first pair generated a ca. 600-bp PCR product with DNA from all SLTI-producing E. coli tested but not from E. coli strains that produce SLTII or variants of SLTII. The second pair generated a ca. 800-bp PCR product with DNA from E. coli strains that produce SLTII or variants of SLTII but not from SLTI-producing E. coli. When used in combination, the SLTI and SLTII oligonucleotide primers amplified DNA from all of the SLT-EC tested. No PCR products were obtained with SLT primers with DNA from 28 E. coli strains that do not produce SLT or 44 strains of 28 other bacterial species. When ground beef samples were inoculated with SLT-EC strains 319 (O157:H7; SLTI and SLTII), H30 (O26:H11; SLTI), and B2F1/3 (O91:H21; SLTII variants VT2ha and VT2hb) and cultured in modified Trypticase soy broth for 6 h at 42 degrees C, an initial sample inoculum of as few as 1 CFU of these SLT-EC strains per g could be detected in PCR assays with DNA extracted from the broth cultures.

Molecular structural basis of ligand selectivity for 5-HT2 versus 5-HT1C cortical receptors

A molecular structural criterion of ligand selectivity for the 5-HT2 versus 5-HT1C receptor was hypothesized on the basis of radioligand binding data. Despite the large number of compounds which have been tested at both receptors, analysis of published data led to the identification of only five agents which are greater than 10-fold selective for the 5-HT2 versus the 5-HT1C receptor. Comparison of the two-dimensional structures revealed that, although these five compounds represent three distinct structural classes, they share a common structural feature located in the region hypothesized to be involved in receptor binding: a carbonyl or carboxyl oxygen interposed spatially between an aromatic ring and nitrogen atom. This structural feature was used to predict the relative selectivity of compounds that had not previously been analyzed at both the 5-HT2 and 5-HT1C receptors. All six drugs tested which contain the identified reactive carbonyl or carboxyl group were found to be selective for the 5-HT2 versus the 5-HT1C receptor with selectivity ratios ranging from 26 to 380. By contrast, three agents which are structurally similar but do not contain the reactive carbonyl or carboxyl group displayed equally high affinity for both receptor binding sites. Since the physiological roles of the 5-HT2 and 5-HT1C receptor are markedly different, it would be of potential clinical and scientific value to utilize this molecular structural feature to further identify chemical compounds which would selectively interact with only one of the two receptors.

Semi-quantitative analysis of early microleakage around amalgam restorations by fluorescent spectrum method: a laboratory study

Rhodamine B, a fluorescent substance, was used as a tracer to investigate in vitro early microleakage from around amalgam restorations in machinable mica glass-ceramic after thermal stress. Five types of amalgam, i.e., low-copper spherical, low-copper lathe-cut, high-copper admixture, high-copper lathe-cut, and high-copper spherical, were examined in the present study. The results indicated that early microleakage from alloys of lathe-cut particles was lower than that from alloys of spherical particles in both low-copper and high-copper amalgam restorations. A high-copper amalgam with a mixture of lathe-cut and spherical particles tended to exhibit the lowest early microleakage.

Myopia in premature infants at the age of 6 months

The authors performed cycloplegic refractions in 180 eyes of 99 premature infants at the age of 6 months to evaluate the incidence and the degree of myopia according to the development and disease course of retinopathy of prematurity (ROP) and to investigate the effect of cryotherapy on the refractive error. The incidences of myopia were not different between premature infants without ROP and premature infants with spontaneously and totally regressed ROP (36.3%, 25.5%), and the degrees of myopia were low in both groups (-1.76 D, -2.25 D). In premature infants with totally regressed ROP after cryotherapy, the incidence of myopia was high (75.5%) but the degree of myopia was low (-3.03 D). In premature infants with cicatricial ROP, cryotreated or not, both the incidence and the degree of myopia were high (93.9%, -5.50 D). It is suggested that cryotherapy increases the incidence of myopia but the degree of myopia induced by cryotherapy is low.

Impact of clinical history on film interpretation

We performed a study to determine whether clinical history gives a positive or negative influence on X-ray film interpretation. One hundred and nine patient's radiograms, consisting of 55 normal and 54 abnormal cases (136 abnormalities), were interpreted twice by three pairs of residents in radiology and a pair of qualified radiologists, without clinical history first and with clinical history next. The interpreters recorded diagnosis and confidence level of normal or abnormal findings on a six-point scale. Analysis of receiver operating characteristic (ROC) curves showed that knowledge of clinical history improved diagnostic accuracy. Residents, especially beginners, should be advised to obtain clinical history whenever they read radiograms.

Tuberculosis, poverty, and "compliance": lessons from rural Haiti

Tuberculosis (TB) is the leading cause of death among rural Haitian adults, and TB control in Haiti is widely acknowledged to be a failure. The causes of both the endemicity of TB and the failure of attempts to address it are briefly reviewed before data from a study conducted in rural, central Haiti are presented. Members of one group of patients with active TB were given free medical care; members of a second group were given free care as well as financial aid, incentives to attend a monthly clinic, and aggressive home follow-up by trained village health workers. Comparing the two groups shows significant differences in mortality, sputum positivity after 6 months of treatment, persistent pulmonary symptoms after 1 year of treatment, average amount of weight gained, ability to return to work, and cure rate. The roles of human immunodeficiency virus and cultural factors are also examined. When adequate nutrition and access to free care were assured, drug-dependent and patient-dependent factors were shown to be of secondary importance in determining treatment outcome. Based on these data from a small, community-based TB-control project, the authors conclude that high cure rates can be achieved if the primacy of economic causes of TB is acknowledged and addressed.

Aromatic hydrocarbon responsiveness-receptor agonists generated from indole-3-carbinol in vitro and in vivo: comparisons with 2,3,7,8-tetrachlorodibenzo-p-dioxin

Indole-3-carbinol (I3C) is a secondary plant metabolite produced in vegetables of the Brassica genus, including cabbage, cauliflower, and brussels sprouts. I3C is both an anti-initiator and a promoter of carcinogenesis. Consumption of I3C by humans and rodents can lead to marked increases in activities of cytochrome P-450-dependent monooxygenases and in a variety of phase II drug-metabolizing enzymes. We have reported previously that the enzyme-inducing activity of I3C is mediated through a mechanism requiring exposure of the compound to the low-pH environment of the stomach. We report here the aromatic hydrocarbon responsiveness-receptor Kd values (22 nM-90 nM), determined with C57BL/6J mouse liver cytosol and the in vitro- and in vivo-molar yields (0.1-6%) of the major acid condensation products of I3C. We also show that indolo[3,2-b]carbazole (ICZ) is produced from I3C in yields on the order of 0.01% in vitro and, after oral intubation, in vivo. ICZ has a Kd of 190 pM for aromatic hydrocarbon responsiveness-receptor binding and an EC50 of 269 nM for induction of cytochrome P4501A1, as measured by ethoxyresorufin O-deethylase activity in murine hepatoma Hepa 1c1c7 cells. The binding affinity of ICZ is only a factor of 3.7 x 10(-2) lower than that of the highly toxic environmental contaminant and cancer promoter 2,3,7,8-tetrachlorodibenzo-p-dioxin. ICZ and related condensation products appear responsible for the enzyme-inducing effects of dietary I3C.

Linker-scanning mutational analysis of the transcriptional activity of the human immunodeficiency virus type 1 long terminal repeat

We have compared the relative importance of transcription regulatory regions in the U3 and R regions of the human immunodeficiency virus type 1 long terminal repeat (LTR) by using linker-scanning mutational analysis. Twenty-six mutant LTR-chloramphenicol acetyltransferase (CAT) transient expression plasmids were prepared in which consecutive 18-bp regions of wild-type LTR were replaced with an NdeI-XhoI-SalI (NXS) polylinker. The mutant LTR-CAT plasmids were transfected into unstimulated Jurkat cells, Jurkat cells stimulated with phytohemagglutinin and tetradecanoylphorbol acetate, and Jurkat cells which constitutively express the human immunodeficiency virus type 1 trans-activator protein, Tat. Transcriptional activity was measured by analysis of CAT activity. The activities of these mutants identified one major and several minor transcription control elements in addition to previously identified elements. In addition, this fine-structure analysis identified differences in utilization of regulatory regions between unstimulated, stimulated, and Tat-expressing Jurkat cells. A significant regulatory region was indicated by linker-scanning mutations between nucleotides -183 and -130 (relative to the transcription start site, +1). These mutations caused marked decreases in activity of the LTR in unstimulated and especially in stimulated Jurkat cells but had no effect in Tat-expressing Jurkat cells. DNA mobility shift studies comparing probes of wild-type and mutant sequences in the -183 to -130 region indicated that alterations in specific DNA binding correspond to the altered transcriptional activity of the mutants. The effects of mutations in several regulatory regions, in addition to the -183 to -130 region described above, differ between Tat-expressing and -nonexpressing Jurkat cells. For example, the NF-kB sites are necessary for transcription in both Tat-expressing and -nonexpressing cells. However, Tat-expressing Jurkat cells primarily require only the 3'-proximal site, while both stimulated and unstimulated Jurkat cells appear to require both sites. Mutants downstream of the TATA element cause a more significant decrease in activity in Tat-expressing Jurkat cells than in the others. Finally, several mutations in the 5' half of the LTR (-453 to -184) show modest increases in transcription (1.5-fold or less) in unstimulated Jurkat cells only, suggesting possible negative regulatory sites. In summary, our studies have identified a control region (-183 to -130) upstream of the NF-kB sites and have more precisely defined significant differences in the utilization of regulatory regions between unstimulated, stimulated, and Tat-expressing Jurkat cells.

Factors affecting the rearrangement efficiency of an Ig test gene

A rearrangement test gene, pHRD, containing the mouse IgH enhancer and the metallothionein promoter, has previously been shown to rearrange efficiently after transfection into a pre-B cell line. Experiments are now reported that assess the requirements of the DNA substrate as well as of the transfected cells for efficient rearrangement. It was found that deletion of the metallothionein promoter or substitution of the IgH enhancer by the kappa enhancer did not affect rearrangement. However, deletion of the Ig enhancer reduced the efficiency. Transfection of pHRD into stable hybrids of pre-B cells and myeloma cells resulted in a high frequency of rearrangement only if certain myeloma chromosomes were lost. Furthermore, pHRD introduced into rearrangement incompetent myeloma cells upon subsequent cell fusion with pre-B cells was rearranged only very rarely and then apparently only immediately after cell fusion. Stable pre-B cell x myeloma hybrids that retained the critical myeloma chromosomes were found to have lost VDJ recombinase activity and transcripts of the RAG-1, RAG-2 and TdT genes. It is concluded that transcription, i.e., the copying of the DNA by polymerase, is probably not required for rearrangement, but that the rearrangement substrate must be in an "open" chromatin state, such as may be provided by transcriptional factors. Furthermore, the absence of rearrangement in myeloma cells is apparently due to the continued action of an inhibitor of rearrangement.

Factors affecting the rearrangement efficiency of an Ig test gene

A rearrangement test gene, pHRD, containing the mouse IgH enhancer and the metallothionein promoter, has previously been shown to rearrange efficiently after transfection into a pre-B cell line. Experiments are now reported that assess the requirements of the DNA substrate as well as of the transfected cells for efficient rearrangement. It was found that deletion of the metallothionein promoter or substitution of the IgH enhancer by the kappa enhancer did not affect rearrangement. However, deletion of the Ig enhancer reduced the efficiency. Transfection of pHRD into stable hybrids of pre-B cells and myeloma cells resulted in a high frequency of rearrangement only if certain myeloma chromosomes were lost. Furthermore, pHRD introduced into rearrangement incompetent myeloma cells upon subsequent cell fusion with pre-B cells was rearranged only very rarely and then apparently only immediately after cell fusion. Stable pre-B cell x myeloma hybrids that retained the critical myeloma chromosomes were found to have lost VDJ recombinase activity and transcripts of the RAG-1, RAG-2 and TdT genes. It is concluded that transcription, i.e., the copying of the DNA by polymerase, is probably not required for rearrangement, but that the rearrangement substrate must be in an "open" chromatin state, such as may be provided by transcriptional factors. Furthermore, the absence of rearrangement in myeloma cells is apparently due to the continued action of an inhibitor of rearrangement.

Analysis of the human immunodeficiency virus long terminal repeat by in vitro transcription competition and linker scanning mutagenesis

Previous studies designed to map the transcriptional regulatory sequences of the human immunodeficiency virus (HIV) long terminal repeat (LTR) have shown disparate results depending on the method of analysis. Experiments have shown that deletions 5' to -104 (relative to the transcription start site, +1) are not required for transcription in vitro, while other experiments have shown that various mutations in this 5' region of the HIV-1 LTR affect both reporter gene activity in transient expression systems and viral growth. To correlate in vitro and in vivo findings, we performed in vitro transcription competition studies to define minimal sequences necessary for competitive factor binding or competitive transcription complex formation. Using normal HeLa cell nuclear extracts, we found that transcription of a reporter gene run by the U3-R region was efficiently competed only by intact LTR DNA fragments representing virtually the entire U3-R region (-453 to +80). Smaller subfragments of the LTR were less effective competitors; these included fragments from -453 to -159, which had a modest competitive ability at higher competitor concentrations, -159 to +80, and -402 to -34, which were both relatively poor competitors. These findings indicate that although the U3-R region truncated to -104 is able to promote in vitro transcription, a more stable transcription complex appears to form on the entire U3-R region. Hence sequences between -453 and -104 appear to be significant in transcription complex formation. In vivo transfection competition studies confirmed these findings. Specific sequences between -453 and -104 which may affect expression or transcription complex formation were mapped using a set of linker-scanning mutants spanning the LTR.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of pilocarpine and atropine administration on radiation-induced injury of rat submandibular glands

In the management of head and neck tumors by radiotherapy, the patients are prone to suffer from radiation-induced damage of the salivary glands. This experiment was carried out to examine the effect of pilocarpine and atropine on the rat submandibular gland and to establish whether it is possible to protect the salivary glands from irradiation by altering the amount of secretory granules in the serous cells prior to irradiation. The submandibular glands of rats were irradiated after pretreatment with or without drugs. Single irradiation of 18 Gy caused significant damage to the submandibular glands without pretreatment, showing the most severe changes 1 week after irradiation and slowly recovering thereafter. Pilocarpine pretreatment was protective against irradiation, displaying much less damage after irradiation of the same dosage, and with complete recovery after 4 weeks. On the other hand, atropine-pretreated animals revealed more extensive damage than the other two groups, possibly due to the retention of secretory granules.

Adjuvant internal hepatic radiotherapy using colloidal 32P chromic phosphate in colorectal cancer

The purpose of the study is to investigate the value of adjuvant radiotherapy given in the form of colloidal chromic phosphate 32P suspension administered via portal vein, in preventing the growth of occult metastases in the liver. Twenty two patients (10 patients of treated group with 12 controls) were followed 12 months after operation. There was no significant change in the CBC and liver functions after administration of 32P labeled colloidal chromic phosphate. Although local recurrence rates were very similar in both groups of colorectal cancer (3/12 in the control group and 4/10 in the treated group), liver metastasis rates were quite different: 4/12 in the control group and none (0/10) in the treated group. In conclusion, 32P labeled colloidal chromic phosphate is expected to prevent liver metastases of completely resected colorectal cancer.