Evaluation of low-level aflatoxin in the diet of white-tailed deer

We evaluated the response of white-tailed deer (WTD) (Odocoileus virginianus) to dietary aflatoxin. Fourteen 4-to-5-mo-old WTD were used in this 8-wk study, conducted between November 1993 and January 1994. Seven animals received a ration containing 800 parts per billion (ppb) total aflatoxin (AF). Seven control animals received the same ration without AF. At 0, 1, 3, 6 and 8 wk, feed consumption, feed conversion, liver enzymes, bile acid levels, and immune function via lymphocyte proliferation assays and delayed type hypersensitivity reactions were determined. At the conclusion of the 8-wk feeding trial, deer were euthanized and necropsied. Clinical illness was not evident in any of the animals, but by the end of the study, AF-fed deer had reduced feed consumption and body weight as compared to control deer; the differences were not statistically significant. The AF-exposed group had a significant increase (P = 0.03) in serum bile acid concentration as compared to control deer. Two AF-exposed deer had gross and histologic hepatic lesions indicative of a mild degenerative hepatopathy. Residues of an aflatoxin metabolite, aflatoxin M1, were found in the livers of all treated animals. No differences in immune function were detected between the two groups. We conclude that consumption of 800 ppb AF in the diet of young WTD over an 8-wk period can produce subclinical hepatic injury.

Efficient delivery of triplex forming oligonucleotides to tumor cells by adenovirus-polylysine complexes

Oligonucleotides (ODNs) show great promise in their ability to specifically inhibit single gene expression but must cross the cell membrane, escape the endosomal vesicle, and possibly traverse the nuclear membrane to arrive at their intracellular target molecules. In an attempt to improve the delivery of phosphodiester triplex forming ODNs to malignant cells, we have constructed adenovirus-polylysine (AdpL)-ODN complexes designed to take advantage of the receptor mediated endocytosis of adenoviruses to transfer the ODNs to the cell nucleus. Treatment of several different types of tumor cells in culture by AdpL-ODN complex resulted in superior uptake and persistence of the ODNs compared to both free ODN and cationic lipid-ODN complexes. Nuclear uptake peaks at 4 h and intact ODN persists in the nucleus with a half-life of 12 h. ODN concentrations of 20-70 microM are achieved at 24 h in all monolayer cell lines evaluated to date. ODNs are detected in 50-100% of the total cell population by immunohistochemistry with apparent uptake into vesicles and nuclear localization. Luciferase expression of a co-delivered reporter plasmid suggests that these ODNs are free in the nucleus. AdpL-ODN complexes will provide a valuable tool for delivering unmodified ODNs to the nucleus of malignant cells.

An automated double staining procedure for bone and cartilage

Differential skeletal staining is an important part of developmental toxicologic studies. Traditionally these studies have required time-consuming differentiation of one or both stains used and careful attention to the maceration step to prevent specimen destruction. We present a fully automated protocol which does not require differentiation of either dye and incorporates a controlled maceration step which is highly reproducible. This has resulted in high quality staining that is reproducible, stable, and can be done in volume with minimal personnel time. The process involves the staining of skinned, eviscerated specimens fixed in 95% ethanol. Using an automated tissue processor, the specimen is stained in alcian blue for 24 hr, macerated in 3% potassium hydroxide for 24 hr and stained with murexide for 24 hr. The specimens are cleared and preserved in glycerol. Within three days specimens have red stained bone and blue stained cartilage. The procedure was developed using 20-day-old Sprague-Dawley rat fetuses to evaluate the feasibility of using the procedure for teratology studies involving the fetal skeleton. Evenly stained specimens can be examined within three days and stored for years without loss of staining.

Evaluation of chemical amendments to reduce ammonia volatilization from poultry litter

Ammonia volatilization from poultry litter often causes high levels of atmospheric ammonia in poultry houses, which is detrimental to both farm workers and birds. Ammonia emissions from houses also aggravate environmental problems, such as acid rain, and result in a loss of fertilizer nitrogen. The objectives of this study were to determine the effect of litter amendments on ammonia volatilization and to determine the effect of these amendments on nitrogen and phosphorus content in litter. The results of this research indicate that alum [Al2(SO4)3.18H2O], ferrous sulfate (FeSO4.7H2O), and phosphoric acid (H3PO4) dramatically reduce ammonia volatilization form litter. The amount of ammonia lost from litter treated with sodium bisulfate (NaHSO4) and a proprietory product made of Ca-Fe silicate with a phosphoric acid coating was not different from the control (untreated litter). Aluminum sulfate (alum) and ferrous sulfate also reduced water soluble P concentrations in litter, whereas phosphoric acid greatly increased water-soluble P levels. The most effective compound evaluated with respect to reducing both ammonia loss and P solubility was alum.

Influence of GC and AT specific DNA minor groove binding drugs on intermolecular triplex formation in the human c-Ki-ras promoter

We have used DNase I footprinting and gel shift assays to characterize the interaction of DNA binding drugs mithramycin, distamycin, and berenil with an intermolecular triplex formed by the human c-Ki-ras promoter. A purine-rich triplex-forming oligonucleotide (ODN) forms a stable intermolecular triple helix (triplex) with a homopurine (PR):homopyrimidine (PY) motif in the human c-Ki-ras promoter which contains a 22bp PR:PY region (-328 to -307). This triplex structure is comprised of 15 G.G:C triplets interspersed with 7 T.A:T triplets. Mithramycin binding sites in the human c-Ki-ras promoter encompass most of the triplex target site and three G-C-rich sequences downstream of this triplex-forming region. Mithramycin binding within the c-Ki-ras promoter completely abrogates triplex formation. Furthermore, the addition of mithramycin to pre-formed triplex by c-Ki-ras promoter displaces the major groove bound ODN. Five prominent distamycin binding sites are noted within the c-Ki-ras promoter including the triplex-forming site as well as A-T-rich regions upstream and downstream of the triplex site. Berenil does not bind within the triplex target sequence, and only one berenil binding sequence downstream of the triplex motif was present within the c-Ki-ras promoter fragment. Neither distamycin nor berenil prevents triplex formation, and, furthermore, the addition of either distamycin or berenil to the pre-formed triplex structure did not displace the major-groove-bound third strand. This study demonstrates that GC-specific and AT-specific minor groove ligands differentially affect the intermolecular pur.pur:pyr triplex. A possible biological significance of mithramycin interaction with intramolecular triplex is discussed.

Intraventricular cryptococcal cysts

The case of a 55-year-old immunocompetent woman with central nervous system cryptococcosis and multiple intraventricular cysts is presented. The cysts did not enhance on MR and had signal characteristics similar to cerebrospinal fluid on T1- and T2-weighted images; their intensity was lower than cerebrospinal fluid on proton density-weighted images.

Human papillomavirus infection: treatment options for warts

Human papillomavirus can produce verrucae, or warts, on cutaneous and mucosal surfaces. Although the diagnosis is usually straightforward, issues regarding the need for treatment and the choice of treatment are complex. The rationale for the treatment of viral warts is based on the prevention of spread to other areas of the body or to other people; the prevention of irritation, bleeding and other unwanted local effects of the wart; cosmetic and psychosocial considerations, and the possible association with neoplasia. A significant proportion of warts resolve spontaneously within two years. Many treatment options appropriate to primary care are available, including local application of salicylic acid, cantharidin, liquid nitrogen and podophyllum. Direct injection of interferon is a choice in selected cases. The decision to treat and the choice of modality must be individualized.

Expression of the unc-4 homeoprotein in Caenorhabditis elegans motor neurons specifies presynaptic input

In the nematode, Caenorhabditis elegans, VA and VB motor neurons arise from a common precursor cell but adopt different morphologies and synapse with separate sets of interneurons in the ventral nerve cord. A mutation that inactivates the unc-4 homeodomain gene causes VA motor neurons to assume the VB pattern of synaptic input while retaining normal axonal polarity and output; the disconnection of VA motor neurons from their usual presynaptic partners blocks backward locomotion. We show that expression of a functional unc-4-beta-galactosidase chimeric protein in VA motor neurons restores wild-type movement to an unc-4 mutant. We propose that unc-4 controls a differentiated characteristic of the VA motor neurons that distinguishes them from their VB sisters, thus dictating recognition by the appropriate interneurons. Our results show that synaptic choice can be controlled at the level of transcription in the post-synaptic neuron and identify a homeoprotein that defines a subset of cell-specific traits required for this choice.

The occurrence of mast cell tumors in young Shar-Peis

During 1991 and 1992, 802 case submissions diagnosed as canine mast cell tumors were submitted to the Athens Veterinary Diagnostic Laboratory. Eighteen of these submissions were from dogs of the Shar-Pei breed. Of these 18 cases, 5 occurred in Shar-Peis less than 2 years of age, 4 of these were poorly differentiated, and 4 out of 5 occurred in the inguinal or preputial area. Three mast cell tumors (grade I) occurred in Boxer/Boxer cross dogs, and 2 tumors (grade II) occurred in Cocker Spaniels younger than 2 years of age. Of the 23,315 histopathology submissions, only 164 were from Shar-Peis and 57 of these dogs were under 2 years of age.

Inhibition of in vitro transcription by a triplex-forming oligonucleotide targeted to human c-myc P2 promoter

Triplex-forming oligonucleotides (TFOs) have been shown to bind in a sequence-specific manner to polypurine/polypyrimidine sequences in several human gene promoters, including the c-myc P1 promoter. TFOs have been shown to inhibit transcription in vitro and the expression of target genes in cell culture. The human c-myc protooncogene contains a 23 base pair purine-pyrimidine-rich motif (-62 to -40) within its predominant promoter, P2, that is a potential target for purine-purine-pyrimidine triplex formation. Using electrophoretic mobility shift analysis (EMSA) and competition experiments, we have demonstrated that a MAZ (myc-associated zinc finger protein) consensus sequence is capable of competing with the purine-pyrimidine motif for the binding of a HeLa nuclear protein. We have shown the formation of an intermolecular triplex using a 23-base purine-rich oligonucleotide antiparallel to the purine-rich target sequence. DNase I footprinting was performed to confirm the exact location of triplex formation. Triplex formation by this oligonucleotide prevents binding of a HeLa nuclear protein (presumably MAZ) to the target site. We have also shown that the P2-targeted TFO is a potent and specific inhibitor of c-myc transcription in vitro. These data demonstrate that this novel TFO inhibits transcription of the c-myc P2 promoter. We propose that the P2-targeted TFO has its effect by blocking the binding of the regulatory factor MAZ.

Expression of beta-galactosidase under the control of the human c-myc promoter in transgenic mice is inhibited by mithramycin

In order to assess the functional contribution of the human c-myc promoter region in the expression of the c-myc gene, transgenic mouse lines containing a bacterial lac Z gene encoding beta-galactosidase under the control of the human c-myc protooncogene promoter were generated. Transgenic mouse embryos heterozygous for the human c-myc Z transgene demonstrate high amounts of beta-galactosidase activity as early as day 11 of embryogenesis by histochemical staining of whole embryos using 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) as substrate, localizing specifically to early spinal cord tissue. beta-galactosidase activity can be demonstrated by histochemical staining in brain tissue of day 14 embryos, localizing mainly to the prefrontal cortex region, while relative amounts of beta-galactosidase in spinal cord tissue are reduced. Determination of specific activity of beta-galactosidase using resorufin-beta-galactopyranoside as substrate in homogenates of whole embryos heterozygous for the human c-myc/lac Z transgene demonstrates significantly elevated beta-galactosidase activity over control embryos in day 11 and day 14 embryos. Surprisingly, cell homogenates of brain tissue from adult G1 generation mice heterozygous for the human c-myc/lac Z transgene demonstrate greater than 10-fold higher specific activity of beta-galactosidase over normal control brain tissue. Specific inhibition of the c-myc/lac Z transgene was also demonstrated in developing embryos using mithramycin given at a dose of 150 micrograms kg-1 d-1 intraperitoneal to pregnant females on days 7-13 of gestation. Both histochemical staining of beta-galactosidase and specific activity assays of day 14 embryos demonstrated significantly lower levels of beta-galactosidase than untreated controls. These results are unique since we are able to detect expression of beta-galactosidase in developing embryonic central nervous system tissue along with adult brain tissue of animals carrying the human c-myc Z transgene and we are able to specifically inhibit expression of the transgene using mithramycin administered in utero.

Inhibition of nuclear protein binding to two sites in the murine c-myc promoter by intermolecular triplex formation

The c-myc gene is overexpressed in a variety of tumor types and appears to play an important role in the abnormal growth of a number of cell types. In an effort to determine the ability of sequence- and species-specific triplex-forming oligonucleotides to inhibit expression of a targeted gene in animals, we have identified two novel triplex-forming sites in the murine c-myc promoter. One is homologous to the triplex-forming human PuF binding element located upstream of the P1 transcription start site. The other triplex-forming site is found in a region between P1 and P2 that encompasses the ME1a1 binding site and part of the E2F binding site and is highly homologous to the human sequence. Synthetic oligodeoxyribonucleotides designed to target these essential regulatory elements form sequence-specific triple helices as demonstrated by gel mobility shift analysis and DNase I footprinting. Polypurine: polypyrimidine regions in the P1 and P2 promoters form specific protein-DNA complexes upon incubation with a murine YC8 nuclear extract. Preincubation of each of the promoter fragments with its respective triplex-forming oligonucleotide results in the inhibition of nuclear protein binding. Non-triplex-forming oligonucleotides do not significantly affect protein binding. The data presented are a preliminary step toward generating an animal model for the phenotypic effects of triplex formation within the c-myc promoter.

Breathing systems reclassified

The purpose of reclassifying breathing systems is to enhance understanding by relating structure to function. A previous classification which appears to fulfill this objective is updated to include recent developments in a newly named group of systems called "displacement afferent reservoir" (DAR) breathing systems. A classification table allows for quick comparison and shows that, of the non-absorber systems, the DAR group has the best characteristics of fresh gas utilization.

An enclosed efferent afferent reservoir system: the Maxima

A single, lightweight, valveless, non-absorber breathing system, which functions with near maximal efficiency (hence the name Maxima) in spontaneous and controlled ventilation is described. It may be classified as an enclosed efferent afferent reservoir (EEAR) breathing system and is characterised by the selective elimination of alveolar gas in all modes of ventilation. A functional description explains how this is achieved in the system in spontaneous and controlled ventilation. The potential for error which arises in combination systems for different switch positions with different modes of ventilation is avoided, as it is a single universal system. With no moving parts, mechanical reliability is guaranteed. The apparatus deadspace is negligible making the system usable even in neonates. Finally, the characteristics of the theoretical ideal non-absorber circuit are discussed as this illustrates the objective of the circuit design and important physical principles surrounding its function.

Comparison in spontaneous ventilation of the Maxima with the Humphrey ADE breathing system and between four methods for detecting rebreathing

An enclosed efferent, afferent reservoir breathing system (Maxima, Life Air Pty Ltd), being valveless, was compared to a simple afferent reservoir system (Humphrey ADE, A mode), having a valve, by assessing fresh gas flow (VF) requirements, with respect to ventilation (VE), that prevents rebreathing in volunteers, awake and breathing spontaneously. The results are recorded in terms of the quotient VF/VE associated with the onset of rebreathing. At the same time four clinical methods for assessing rebreathing were evaluated from the perspective of suitability for practical application during anaesthesia. No significant difference was found in the VF requirements between the ADE and Maxima breathing systems with respective values obtained for the quotient VF/VE of 0.80 and 0.77. Our findings showed that the method of sampling carbon dioxide (CO2) at the outflow of the efferent limb of the patient connector (eliminated CO2 method) in both afferent reservoir systems provided the highest flow rate and most reliable indication for detecting potential or actual rebreathing, when attempting to minimize VF. It provides no additional deadspace or resistance to gas flow, and has the advantage of being the only qualitative method that is reliable for the purpose of detecting the onset of rebreathing.

Maxima and Bain breathing systems compared in controlled ventilation

The Maxima is a new universal breathing system, which, despite its being valveless, functions with near maximal efficiency in spontaneous and controlled ventilation. It was compared to the Bain system in controlled ventilation by adjusting fresh gas flows (VF) to achieve an end-tidal CO2 of 5% in 40 patients aged from one to seventy-six years. They received a combined regional and general anaesthetic technique. The overall VF requirement of the Maxima system was: weight in kg x 35 ml.min-1.kg-1 + 1160 ml.min-1; the Bain system required VF of: weight in kg x 42 ml.min-1.kg-1 + 2070 ml.min-1. The mean VF requirement for the Bain system was greater by 45%. Of these forty patients, the results from the twenty-four adult patients weighing 50 kg or more gave the respective VF requirements for the Maxima and Bain systems of 52 and 71 ml.min-1.kg-1. In a separate study using twenty-nine patients, the fractional utilization of fresh gas (FU) (or VAe/VF where VAe = effective alveolar ventilation) in the Maxima and Bain systems was shown to be 0.94 and 0.71 respectively.

Epidermal growth factor secreted from the salivary gland is necessary for liver regeneration

Partial hepatectomy (PH) in rats induces a synchronized burst of DNA replication in the remnant liver that peaks at 24 h post-PH. We report here that removal of the major salivary glands before one-third and two-thirds PH prevents the proliferative response in the remaining liver. Twelve days after one-third PH, the remnant liver is 89% of the normal liver weight in nonsalivectomized rats but only 55% in salivectomized animals. This indicates that salivectomy does not merely delay the first round of cell division but that it prevents actual regeneration. Salivectomy alters the early protooncogene response to partial hepatectomy. In salivectomized rats, the characteristic peak of c-myc mRNA synthesis at 2-4 h after PH is significantly decreased compared with nonsalivectomized rats. The peak of DNA synthesis at 24 h after PH in salivectomized rats is also dramatically decreased. DNA synthesis as measured by [3H]thymidine incorporation into DNA of hepatic cells is decreased approximately 90% in salivectomized rats vs. nonsalivectomized rats 22-26 h after PH. Ligation of the venous drainage of the salivary gland results in the same inhibitory effect on DNA synthesis, indicating 1) that the salivary gland must release circulating factor(s), and 2) that the early increase in c-myc expression and the subsequent DNA synthesis, both of which reflect the stimulation of cellular proliferation in the regenerating liver, are induced by humoral factor(s) released from the salivary glands. Injection of exogenous epidermal growth factor (EGF) in salivectomized rats results in restoration of both the DNA synthetic and c-myc responses at levels characteristic of those of liver regeneration.(ABSTRACT TRUNCATED AT 250 WORDS)

The c-myc promoter binding protein (MBP-1) and TBP bind simultaneously in the minor groove of the c-myc P2 promoter

The c-myc promoter binding protein (MBP-1) is a DNA binding protein which negatively regulates the expression of the human c-myc gene. MBP-1 binds to a sequence which overlaps the binding site for the general transcription factor TBP, within the c-myc P2 promoter region. Since TBP binds in the minor groove, MBP-1 might inhibit c-myc transcription by preventing the formation of a functional preinitiation complex. In support of this hypothesis, we have demonstrated that MPB-1 is a minor groove binding protein. In order to characterize MBP-1 binding, we substituted A-T base pairs in the MBP-1 binding site with I-C base pairs, which changes the major groove surface without altering the minor groove surface. This substitution did not inhibit the sequence-specific binding of MBP-1 and TBP. On the other hand, G-C to I-C substitution within the MBP-1 binding site alters the minor groove and prevents MBP-1 binding. Competitive electrophoretic mobility shift assays were used to show that berenil, distamycin, and mithramycin, all of which bind in the minor groove, compete with MBP-1 for binding to the MPB-1 binding site. These minor groove binding ligands also effectively inhibit the simultaneous DNA binding activity of both MBP-1 and TBP. We conclude that both MBP-1 and TBP can bind simultaneously in the minor groove of the TATA motif on the c-myc P2 promoter. This suggests that MBP-1 may negatively regulate c-myc gene expression by preventing efficient transcription initiation.

Mithramycin inhibits myointimal proliferation after balloon injury of the rat carotid artery in vivo

BACKGROUND

Smooth muscle proliferation and extracellular matrix formation in the subintimal region of blood vessels that have been subjected to intimal injury are responsible for restenosis following balloon angioplasty of the coronary arteries and for accelerated atherosclerosis in a variety of other pathophysiological states. The immediate early-response gene c-myc is overexpressed in proliferating vascular smooth muscle cells in vitro, and c-myc antisense oligomers have been shown to reduce c-myc expression and to inhibit proliferation of vascular smooth muscle cells in culture. Mithramycin is a commercially available G-C-specific DNA binding drug that selectively inhibits transcription of genes, such as c-myc, that have G-C-rich promoter sequences. This study tested the hypothesis that mithramycin inhibits transcription of the c-myc proto-oncogene and prevents myointimal proliferation after balloon injury of the rat carotid artery in vivo.

METHODS AND RESULTS

Ten-week-old male Sprague-Dawley rats received mithramycin (150 micrograms/kg IP) or distilled H2O 1 hour before and 1 hour after balloon injury of the right common carotid artery. After 2 weeks, the rats were killed by overdose of pentobarbital, and the injured right and uninjured control left arteries were pressure-fixed and subjected to morphological analysis for evaluation of the degree of myointimal thickening. Separate groups of rats were killed at 2 and 6 hours after vascular injury, and total RNA from injured and control vessels of mithramycin- and vehicle-treated rats was subjected to Northern analysis for assessment of steady-state c-myc mRNA levels. The areas of neointima and the ratios of neointimal to medial area were significantly less in mithramycin-treated than in control rats (0.6 +/- 0.1 versus 1.2 +/- 0.1 mm2, P < .01 and 95 +/- 16% versus 190 +/- 14%, P < .01). Lumen size was significantly greater in mithramycin-treated than in control rats (1.5 +/- 0.1 versus 0.8 +/- 0.1 mm2, P < .01). Steady-state c-myc mRNA levels were increased 10-fold and 2-fold (compared with undamaged carotid arteries) at 2 and 6 hours after balloon injury, respectively; mithramycin treatment reduced c-myc mRNA levels at 2 and 6 hours by 66% and 53%, respectively.

CONCLUSIONS

These results support the hypothesis that systemic administration of mithramycin immediately (1 hour before and after intervention effectively inhibits transcription of the c-myc proto-oncogene and prevents myointimal proliferation after balloon injury of the rat carotid artery in vivo. Because mithramycin has been shown to be well tolerated by humans and to effectively inhibit transcription of c-myc in proliferating human cells, this agent may be useful in the prevention of coronary restenosis.

The conjunctival wart: report of a case and review of treatment options

Human papillomavirus, a papovavirus, is the causative agent of all warts. There are at least 63 subtypes of this virus, certain ones of which are more likely to cause warts in particular locations or to be associated with malignancies. Over the last 6 years, HPV-6, HPV-11, and HPV-16 have been detected in both benign and malignant lesions of the conjunctiva. We report a patient with a large viral papilloma of the palpebral conjunctiva of the right lower eyelid. This case demonstrates that even very large viral papillomas can be treated successfully.

A practical approach to antibiotic treatment in women taking oral contraceptives

Clinical situations that require the use of systemic antibiotic therapy are common. Because millions of women choose oral contraceptives for birth control, the potential for interaction between these drugs frequently has to be considered. We review the available information and present a practical approach for dealing with this situation based on sharing responsibility with an educated patient.

The G-C specific DNA binding drug, mithramycin, selectively inhibits transcription of the C-MYC and C-HA-RAS genes in regenerating liver

Expression of the c-myc and c-Ha-ras protooncogenes is dramatically increased in regenerating rat liver as an early response to partial hepatectomy. Nuclear runon transcription studies confirm that the increased c-myc and c-Ha-ras mRNA levels in regenerating livers reflect transcriptional activation of these genes. Mithramycin, a G-C specific DNA binding drug, prevents the increased transcriptional activity of c-myc and c-Ha-ras genes after hepatectomy but does not alter the transcriptional activity of the beta-actin gene. Continuous exposure of rats to mithramycin after hepatectomy prevents the increase in both c-myc and c-Ha-ras expression and blocks the increased cellular proliferation characteristic of regeneration. The delayed increase in c-myc and c-Ha-ras gene expression is associated with a delay in cellular proliferation. The inhibition of c-myc and c-Ha-ras transcription by mithramycin, the delay in cellular proliferation, and the ability of mithramycin to prevent protein binding to the c-myc promoter, suggest that the increased expression of these genes is a necessary component of liver regeneration.

Urinary porphyrins as biological indicators of oxidative stress in the kidney. Interaction of mercury and cephaloridine

Reduced porphyrins (hexahydroporphyrins, porphyrinogens) are readily oxidized in vitro by free radicals which are known to mediate oxidative stress in tissue cells. To determine if increased urinary porphyrin concentrations may reflect oxidative stress to the kidney in vivo, we measured the urinary porphyrin content of rats treated with mercury as methyl mercury hydroxide (MMH) or cephaloridine, both nephrotoxic, oxidative stress-inducing agents. Rats exposed to MMH at 5 ppm in the drinking water for 4 weeks showed a 4-fold increase in 24-hr total urinary porphyrin content and a 1.3-fold increase in urinary malondialdehyde (MDA), an established measure of oxidative stress in vivo. Treatment with cephaloridine alone (10-500 mg/kg, i.p.) produced a dose-related increase in urinary MDA and total porphyrin levels up to 1.6 and 7 times control values, respectively. Injection of MMH-treated rats with cephaloridine (500 mg/kg) caused a synergistic (20-fold) increase in urinary porphyrin levels, but an additive (1.9-fold) increase in the MDA concentration. Studies in vitro demonstrated that cephaloridine stimulated the iron-catalyzed H2O2-dependent oxidation of porphyrinogens to porphyrins in the absence of either microsomes or mitochondria. Additionally, porphyrinogens were oxidized to porphyrins in an iron-dependent microsomal lipid peroxidation system. Moreover, porphyrinogens served as an effective antioxidant (EC50 approximately 1-2 microM) to lipid peroxidation. These results demonstrate that MMH and cephaloridine synergistically, as well as individually, promote increased oxidation of reduced porphyrins in the kidney and that this action may be mechanistically linked to oxidative stress elicited by these chemicals. Increased urinary porphyrin levels may, therefore, represent a sensitive indicator of oxidative stress in the kidney in vivo.

Dominant unc-37 mutations suppress the movement defect of a homeodomain mutation in unc-4, a neural specificity gene in Caenorhabditis elegans

The unc-4 gene of Caenorhabditis elegans encodes a homeodomain protein that defines synaptic input to ventral cord motor neurons. unc-4 mutants are unable to crawl backward because VA motor neurons are miswired with synaptic connections normally reserved for their sister cells, the VB motor neurons. These changes in connectivity are not accompanied by any visible effects upon neuronal morphology, which suggests that unc-4 regulates synaptic specificity but not axonal guidance or outgrowth. In an effort to identify other genes in the unc-4 pathway, we have devised a selection scheme for rare mutations that suppress the Unc-4 phenotype. We have isolated four, dominant, extragenic, allele-specific suppressors of unc-4(e2322ts), a temperature sensitive allele with a point mutation in the unc-4 homeodomain. Our data indicate that these suppressors are gain-of-function mutations in the previously identified unc-37 gene. We show that the loss-of-function mutation unc-37(e262) phenocopies the Unc-4 movement defect but does not prevent unc-4 expression or alter VA motor neuron morphology. These findings suggest that unc-37 functions with unc-4 to specify synaptic input to the VA motor neurons. We propose that unc-37 may be regulated by unc-4. Alternatively, unc-37 may encode a gene product that interacts with the unc-4 homeodomain.

Cimetidine QID and BID in rapid heartburn relief and healing of lesions in gastroesophageal reflux disease

This multicenter, double-blind, randomized, placebo-controlled trial investigated QID and BID regimens of cimetidine (total daily dosage of 1600 mg) in adult patients with moderate or severe gastroesophageal reflux disease. Healing of endoscopically documented lesions and heartburn pain relief were compared among three treatment groups: placebo (n = 82), cimetidine 800 mg BID (n = 85), and cimetidine 400 mg QID (n = 83). To maintain the double-blind conditions, all groups received two tablets QID (a combination of placebo and drug). Healing and improvement were evaluated with repeat endoscopy at 6 and 12 weeks, and pain severity for daytime and nighttime heartburn was recorded separately on diary cards and was rated on a four-point scale (severe = 3, moderate = 2, mild = 1, or none = 0). Efficacy results for the three treatment groups are presented in the following order: placebo, cimetidine 800 mg BID, and cimetidine 400 mg QID. Cumulative healing at week 12, using life-table methods, was 42%, 60% (P < 0.05 vs placebo), and 66% (P < 0.01 vs placebo), respectively. Cumulative improvement was 49%, 66% (P < 0.05 vs placebo), and 75% (P < 0.01 vs placebo), respectively. Median time in days to achieve 24 hours of complete freedom from heartburn was 18, 9, and 4 (P < 0.01 vs placebo), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Triplex formation inhibits HER-2/neu transcription in vitro

Triplex-forming oligonucleotides (TFOs) have been shown to bind to target DNA sequences in several human gene promoters such as the c-myc oncogene, the epidermal growth factor receptor, and the dihydrofolate reductase genes. TFOs have been shown to inhibit transcription in vitro and gene expression in cell culture of the c-myc and other genes. The HER-2/neu oncogene, which is overexpressed in breast cancer and other human malignancies, contains a purine-rich sequence in its promoter, which is favorable for purine:purine:pyrimidine (R:R:Y) triplex formation. Although its function in the HER-2/neu promoter is unknown, this purine-rich site is homologous to a protein-binding sequence in the promoter of the epidermal growth factor receptor that is necessary for efficient transcription of this gene. We have shown that this sequence is a site for nuclear protein binding by incubation with a crude nuclear extract. We describe the formation of an interstrand triplex using a purine-rich oligonucleotide antiparallel to this purine-rich target sequence of the HER-2/neu promoter. Triplex formation by the oligonucleotide prevents protein binding to the target site in the HER-2/neu promoter in vitro. We have shown that this oligonucleotide is a potent and specific inhibitor of HER-2/neu transcription in an in vitro assay. The triplex target site contains a single pyrimidine base that does not conform to the R:R:Y triplex motif. In an attempt to abrogate the potentially destabilizing effects of this pyrimidine base on triplex formation, we have substituted an abasic linker for the pyrimidine residue in the triplex forming oligonucleotide. Triplex formation with the modified oligonucleotide appears to occur with approximately equivalent binding affinity. Triplex formation in the HER-2/neu oncogene promoter prevents transcription in vitro and may represent a future modality for specific inhibition of this gene in vivo.

A multiple modality approach combining the effect of conditioning with adoptive chemoimmunotherapy

It has been demonstrated that significant protection against YC8 lymphoma can be induced in mice preimmunized with normal DBA/2 spleen cells. The DBA/2 spleen cells used as an alloantigen share minor histocompatibility determinants with the YC8 tumor. Our observations showed that once tumor was present in vivo, the use of a potent tumor specific vaccine that can confer 100% protection to preimmunized animals, can help in increasing survival but can no longer produce high incidence of regression and cure. We have used this model to show that adoptive chemoimmunotherapy (ACIT) can be used to regress tumors in mice with large body burden of tumor and that combination of conditioning with ACIT appears to enhance the effectiveness of treatment. The nature of the immunity conferred by conditioned resistance might be due to cytotoxic T-lymphocytes.

Redox activities of mercury-thiol complexes: implications for mercury-induced porphyria and toxicity

Mercury exposure causes oxidative damage to the kidney, resulting in numerous biochemical changes, including the excretion of excess porphyrins in the urine (porphyrinuria). Hg(II)-induced porphyrinuria may occur, in part, by the previously reported oxidation of reduced porphyrins (porphyrinogens) by a GSH/Hg(II) complex and H2O2. To further elucidate the mechanism(s) of porphyrinogen oxidation by GSH, Hg(II), and H2O2, we compared the ability of several thiol compounds and peroxides to substitute for GSH or H2O2, respectively, in the oxidation of uroporphyrinogen (urogen). Every thiol compound tested resulted in enhanced urogen oxidation in the presence of Hg(II) and H2O2, albeit at different rates. Additionally, t-butyl or cumene hydroperoxide substituted for H2O2 in promoting urogen oxidation, although neither peroxide was as effective in this regard. Mercury-thiol complexes synthesized from Hg(I) and GSSG also promoted urogen oxidation in the presence of H2O2. Additionally, in the absence of urogen, both GSH/Hg(II) or GSSG/Hg(I) catalyzed the decomposition of H2O2. Finally, incubation of GSH/Hg(II) or GSSG/Hg(I) with H2O2 resulted in HPLC-detectable products distinct from GSH, GSSG, or GS2Hg(II). These findings suggest that mercury-thiol complexes possess redox activity in biological systems, which promotes the oxidation of porphyrinogens and possibly other biomolecules.

A unique c-myc-targeted triplex-forming oligonucleotide inhibits the growth of ovarian and cervical carcinomas in vitro

A 27-base pair triplex forming oligonucleotide (G27-oligonucleotide) targeted to the "puf" regulatory protein-binding domain of the human c-myc oncogene has been conjugated with the DNA-binding molecule acridine (G27-conjugate) in order to obtain a drug with high binding affinity as well as high sequence specificity. Both the triplex-forming oligonucleotide and its acridine conjugate are shown to form triple-stranded DNA at the site of the target sequence by DNase 1 footprinting. When the cervical carcinoma cell line HeLa was exposed to 4 microM concentrations of the G27-oligonucleotide the viable cell count fell to 89, 56, and 49% of control at 25, 50, and 72 hr. After exposure to 1 microM G27-conjugate the viable cell count fell to 87, 50, and 33% of control. Nonspecific reductions in cell number were found for the control oligonucleotides to 79 and 82% of control. When SKOV-3 cells were exposed to the same concentrations of oligonucleotides, viable cell count in relation to control fell to 43, 50, and 67% with the G27-oligonucleotide and 57, 52, and 53% with the G27-conjugate at 24, 48, and 72 hr. The control oligonucleotides again caused a small nonspecific drop in the viable cell number.

Studies on Hg(II)-induced H2O2 formation and oxidative stress in vivo and in vitro in rat kidney mitochondria

Studies were undertaken to investigate the principal actions underlying mercury-induced oxidative stress in the kidney. Mitochondria from kidneys of rats treated with HgCl2 (1.5 mg/kg i.p.) demonstrated a 2-fold increase in hydrogen peroxide (H2O2) formation for up to 6 hr following Hg(II) treatment using succinate as the electron transport chain substrate. No increase in H2O2 formation was observed when NAD-linked substrates (malate/glutamate) were used, suggesting that Hg(II) affects H2O2 formation principally at the ubiquinone-cytochrome b region of the mitochondrial respiratory chain in vivo. Together with increased H2O2 formation, mitochondrial glutathione (GSH) content was depleted by more than 50% following Hg(II) treatment, whereas formation of thiobarbiturate reactive substances (TBARS), indicative of mitochondrial lipid peroxidation, was increased by 68%. Studies in vivo revealed a significant concentration-related depolarization of the inner mitochondrial membrane following the addition of Hg(II) to mitochondria isolated from kidneys of untreated rats. This effect was accompanied by significantly increased H2O2 formation, GSH depletion and TBARS formation linked to both NADH dehydrogenase (rotenone-inhibited) and ubiquinone-cytochrome b (antimycin-inhibited) regions of the electron transport chain. Oxidation of pyridine nucleotides (NAD[P]H) was also observed in mitochondria incubated with Hg(II) in vitro. In further studies in vitro, the potential role of Ca2+ in Hg(II)-induced mitochondrial oxidative stress was investigated. Ca2+ alone (30-400 nmol/mg protein) produced no increase in H2O2 and only a slight increase in TBARS formation when incubated with kidney mitochondria isolated from untreated rats. However, Ca2+ significantly increased H2O2 and TBARS formation elicited by Hg(II) at the ubiquinone-cytochrome b region of the mitochondrial electron transport chain, whereas TBARS formation was decreased significantly when the Ca2+ uptake inhibitors, ruthenium red or [ethylenebis(oxyethylenenitrilo)]tetraacetic acid (EGTA), were included with Hg(II) in the reaction mixtures. These findings support the view that Hg(II) causes depolarization of the mitochondrial inner membrane with consequent increased H2O2 formation. These events, coupled with Hg(II)-mediated GSH depletion and pyridine nucleotide oxidation, create an oxidant stress condition characterized by increased susceptibility of mitochondrial membranes to iron-dependent lipid peroxidation (TBARS formation). Since increased H2O2 formation, GSH depletion and lipid peroxidation were also observed in vivo following Hg(II) treatment, these events may underlie oxidative tissue damage caused by mercury compounds. Moreover, Hg(II)-induced alterations in mitochondrial Ca2+ homeostasis may exacerbate Hg(II)-induced oxidative stress in kidney cells.

The Miller tracheal cuff pressure control valve. Clinical use in controlled and spontaneous ventilation

A constant pressure differential valve for the control of tracheal tube cuff pressure was tested under clinical conditions. Fifty-one patients underwent controlled ventilation and 20 patients were allowed to breathe spontaneously. Nitrous oxide 66% with oxygen 33% and halothane were used via a circle system. With controlled respiration at a fresh gas flow of 3-10 l.min-1, the expiratory cuff pressures of 10.1-16 cmH2O and the inspiratory cuff pressures of 23.4-32.4 cmH2O were below venous and arterial mucosal capillary perfusion pressures respectively. Cuff pressures were unaltered with time. Methylene blue instilled into the larynx did not appear in the trachea. Fifty-two control patients had the same incidence of sore throat (40%) and hoarseness (30%) at 24 h. With spontaneous ventilation, fresh gas flows of 5-15 l.min-1 maintained the cuff pressure above 10 cmH2O. We conclude that this valve prevents excessive tracheal cuff pressure while maintaining the airway seal.

The role of metals in the enzymatic and nonenzymatic oxidation of epinephrine

The effects of transition metals on nonenzymatic and ceruloplasmin catalyzed epinephrine oxidation were investigated by studying rates of epinephrine oxidation in purified buffers and in the presence of metal chelating agents. We found that epinephrine does not "autoxidize" in sodium chloride solutions prepared with deionized water that was further purified by chromatography over Chelex 100 resin prior to use. Epinephrine was oxidized rapidly in sodium chloride prepared with tap water (1.20 +/- 0.12 nmoles/min) or in deionized water (0.40 +/- 0.80 nmoles/min), but this oxidation was prevented by the addition of Desferal, a potent metal chelating agent. Epinephrine oxidation was enhanced upon the addition of ceruloplasmin, and this oxidation rate could be slowed, but not eliminated, by the addition of Desferal. If epinephrine solutions were preincubated for 72 hours with Desferal prior to ceruloplasmin addition, however, no oxidation was observed. Epinephrine was shown to form colored complexes with both iron and copper at pH 7.0. The Fe(III)-epinephrine complex was much more stable than was the Cu(II)-epinephrine complex. Oxygen consumption studies of ceruloplasmin catalyzed epinephrine oxidation showed that copper was a better promoter of epinephrine oxidation than was iron, suggesting that ceruloplasmin-catalyzed epinephrine oxidation results from adventitious copper bound to the purified enzyme. In light of these results, the physiological relevance of ceruloplasmin catalyzed oxidation of biogenic amines may be minor.

Xanthine oxidase- and iron-dependent lipid peroxidation

Xanthine oxidase and iron-dependent lipid peroxidation has been studied extensively in many model systems, yet several details of this process remain unclear. Because redox reactions of iron are important parameters of iron-catalyzed lipid peroxidation, we have examined the roles of superoxide and hydrogen peroxide, produced by xanthine oxidase, to oxidize and reduce iron and thereby affect iron-catalyzed lipid peroxidation. Thus, we compared lipid peroxidation catalyzed by xanthine oxidase and ADP:Fe(III) to that catalyzed by xanthine oxidase and ADP:Fe(II). An examination of the action of superoxide on iron oxidation and reduction revealed that superoxide is a better oxidant of ADP:Fe(II) than a reductant of ADP:Fe(III). A superoxide generating system (composed of xanthine oxidase and catalase) and ADP:Fe(II) also resulted in a greater amount of lipid peroxidation than superoxide and ADP:Fe(III). Hydrogen peroxide, as expected, only served as an Fe(II) oxidant. A comparison of the oxidant activities of either superoxide or hydrogen peroxide on ADP:Fe(II) and the corresponding effects on lipid peroxidation revealed that both oxidants were roughly equivalent. We conclude that superoxide and hydrogen peroxide, produced from xanthine oxidase, support iron-catalyzed lipid peroxidation through their participation in redox reactions of iron, that is, they facilitate Fe(II) oxidation or Fe(III) reduction necessary for lipid peroxidation. The relevance of the reactions of O2-. and H2O2 on physiological chelates of iron are discussed.

Structure and applications of intermolecular DNA triplexes

Current DNA binding drugs are not sequence specific. Triplex-forming oligonucleotides will bind targeted duplex DNA sites in a sequence-specific manner. A new class of DNA binding molecules based on triple-helical DNA formation promises a sequence-specific method of targeting discrete regions of DNA. DNA modifying molecules linked to third strands have been shown to modify only regions of DNA to which they were targeted. Current research will increase the understanding of triplex DNA structure and will lead to improved DNA binding drugs.

The best asthma care. A case problem in continuous quality improvement

In the future, health care delivery systems may need to respond to requests from payers to demonstrate the quality of care they provide for types of patients or diseases. Here, asthma is used as an example of what such a response might look like in the context of continuous quality improvement.

Phase I trial of the murine monoclonal anti-GD2 antibody 14G2a in metastatic melanoma

In a phase I trial, 12 patients with GD2 antigen-positive metastatic melanoma received the murine anti-GD2 monoclonal antibody 14G2a. The monoclonal antibody was administered in four doses over an 8-day period with total dose ranging from 10 to 120 mg. All patients receiving greater than 10 mg of 14G2a experienced transient abdominal/pelvic pain during the antibody infusion. Five patients had a delayed extremity pain syndrome following the third and fourth antibody infusion. Four of the five patients developed neurological toxicity, including two patients with significant although reversible motor neuropathy. Two of the patients developed hyponatremia secondary to a syndrome of inappropriate antidiuretic hormone. All 12 patients developed high levels of human anti-14G2a antibody. The plasma half-life of 14G2a was 42 +/- 6 (SD) h. One patient each had a partial response, mixed response, and stable disease, respectively. The very modest antitumor activity accompanied by dose-limiting neurological toxicity at total doses greater than 80 mg may restrict the clinical utility of murine 14G2a.

A pressure regulator for the cuff of a tracheal tube

A regulator is described for the maintenance of a constant pressure difference above airway pressure during positive pressure ventilation in a cuffed tracheal tube. It comprises a tubular threshold valve which is powered by the anaesthetic gas supply source to a breathing system. The valve is interposed between the anaesthetic gas supply machine and the breathing system creating a pressure differential. The upstream pressure is transmitted to the pilot tube supplying the cuff of a tracheal tube via an upstream connection. The valve is suitable only for breathing systems that require a constant gas supply. The regulator was evaluated during anaesthesia, using a modified Mallinkrodt Hi-Lo jet ventilation tube to obtain simultaneous pressure measurements within the cuff and the lumen of the tracheal tube. A greater pressure was demonstrated in the cuff than in the airway and the two traces were approximately parallel throughout the respiratory cycle. The device should prevent excessive cuff inflation pressure and solves the problem of forgetting to let the cuff down before extubation.

Expression and regulation of the cystic fibrosis gene during rat liver regeneration

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) are responsible for cystic fibrosis. The CFTR gene has recently been identified and encodes a 6.5-kb mRNA transcript. Recent observations showing that CFTR expression increases during differentiation of epithelial cells suggested that CFTR may also be regulated in the liver in response to partial hepatectomy (PH). We studied the expression of CFTR in rat regenerating liver and investigated the mechanisms that regulate CFTR RNA levels during a 120-h period after PH. Northern and slot-blot analysis revealed a liver-specific biphasic increase of CFTR mRNA levels, which peaks at 2 and 24 h post-PH. In contrast to these findings, the mode of regulation of the homologous gene MDR-1 showed a clearly different pattern. Nuclear run-on analysis demonstrated increased levels of CFTR transcription corresponding to the time points where an increase in CFTR message was observed. Similarly, the beta-actin gene, which increases transiently during liver regeneration, showed increased nuclear run-on activity 4 h posthepatectomy, indicating that the nuclei were functional. No increase of MDR-1 gene transcription was detected, confirming the previous finding that the increase in MDR-1 mRNA level in regenerating liver results from a post-transcriptional event such as message stabilization. This study indicates that expression of the CFTR gene is regulated during the regenerative process of the liver. The data also suggest that the increase in CFTR and MDR expression levels result from two distinct regulatory mechanisms.

Recombinant bovine rhodanese: purification and comparison with bovine liver rhodanese

Recombinant bovine rhodanese (thiosulfate: cyanide sulfurtransferase, EC 2.8.1.1) has been purified to homogeneity from Escherichia coli BL21(DE3) by cation-exchange chromatography. Recombinant and bovine liver rhodanese coelectrophorese under denaturing conditions, with an apparent subunit molecular weight of 33,000. The amino terminal seven residues of the recombinant protein are identical to those of the bovine enzyme, indicating that E. coli also removes the N-terminal methionine. The Km for thiosulfate is the same for the two proteins. The specific activity of the recombinant enzyme is 12% higher (816 IU/mg) than that of the bovine enzyme (730 IU/mg). The two proteins are indistinguishable as to their ultraviolet absorbance and their intrinsic fluorescence. The ability of the two proteins to refold from 8 M urea to enzymatically active species was similar both for unassisted refolding, and when folding was assisted either by the detergent, lauryl maltoside or by the E. coli chaperonin system composed of cpn60 and cpn10. Bovine rhodanese is known to have multiple electrophoretic forms under native conditions. In contrast, the recombinant protein has only one form, which comigrates with the least negatively charged of the bovine liver isoforms. This is consistent with the retention of the carboxy terminal residues in the recombinant protein that are frequently removed from the bovine liver protein.

Triplex formation prevents Sp1 binding to the dihydrofolate reductase promoter

The human dihydrofolate reductase (DHFR) promoter sequence contains two consensus binding sites for the Sp1 regulatory protein. We have determined the effect of intermolecular triplex DNA formation on Sp1 binding to the DHFR promoter. The DHFR Sp1 binding site I (-39 to -48 relative to the DHFR transcription start site) demonstrates concentration-dependent triplex formation with a 19-base pair G-rich oligonucleotide (GR19) which is complementary to the polypyrimidine strand. DNase I footprint analysis demonstrates that GR19 forms a DNA triplex structure with the DHFR promoter fragment in a sequence-specific manner. DNase I footprinting analysis also indicates that the orientation of binding of these G-rich oligonucleotides is antiparallel. CR19, a C-rich complementary oligonucleotide, on the other hand, does not form triplex. The DNase I protection pattern of DHFR promoter fragment incubated with both recombinant Sp1 and triplex-forming oligonucleotide suggests that triplex formation prevents Sp1 binding. This is confirmed by gel shift analysis which demonstrates that triplex formation by the Sp1 binding sequences of the DHFR promoter prevents recombinant Sp1 binding in a concentration-dependent manner. These results demonstrate that intermolecular triplex formation prevents regulatory protein binding in a sequence-specific manner.

Effects of deferrioxamine on iron-catalyzed lipid peroxidation

The kinetics of iron binding by deferrioxamine B mesylate and the ramifications of this process upon iron-catalyzed lipid peroxidation were assessed. The relative rates of Fe(III) binding by deferrioxamine varied for the chelators tested as follows: ADP greater than AMP greater than citrate greater than histidine greater than EDTA. The addition of a fivefold molar excess of deferrioxamine to that of Fe(III) did not result in complete binding (within 10 min) for any of the Fe(III) chelates tested except ADP:Fe(III). The rates of Fe(III) binding by deferrioxamine were greater at lower pH and when the competing chelator concentration was high in relationship to iron. The relatively slow binding of Fe(III) by deferrioxamine also affected lipid peroxidation, an iron-dependent process. The addition of deferrioxamine to an ascorbate- and ADP:Fe(III)-dependent lipid peroxidation system resulted in a time-dependent inhibition or stimulation of malondialdehyde formation (i.e., lipid peroxidation), depending on the ratio of deferrioxamine to iron. Converse to Fe(III), the rates of Fe(II) binding by deferrioxamine from the chelators tested above were rapid and complete (within 1 min), and resulted in the oxidation of Fe(II) to Fe(III). Lipid peroxidation dependent on Fe(II) autoxidation was stimulated by the addition of deferrioxamine. Malondialdehyde formation in this system was inhibited by the addition of catalase, and a similar extent of lipid peroxidation was achieved by substituting hydrogen peroxide for deferrioxamine. Collectively, these results suggest that the kinetics of Fe(III) binding by deferrioxamine is a slow, variable process, whereas Fe(II) binding is considerably faster. The binding of either valence of iron by deferrioxamine may result in variable effects on iron-catalyzed processes, such as lipid peroxidation, either via slow binding of Fe(III) or the rapid binding of Fe(II) with concomitant Fe(II) oxidation.

Infertility in a ewe as a result of ovotestis

A ewe with apparently normal estrous cycles was unable to conceive as a result of a single ovotestis. The ovotestis was diagnosed on the basis of results from laparoscopic examination, human chorionic gonadotropin stimulation, and histologic examination of the gonad. The report reinforces the necessity of considering all causes of infertility in affected sheep, and not simply infective causes.

Characterization of the binding of transforming growth factor-beta 1, -beta 2, and -beta 3 to recombinant beta 1-latency-associated peptide

Preprotransforming growth factor-beta 1 (TGF beta 1) is a 390-amino acid precursor polypeptide that undergoes a number of processing steps to yield mature TGF beta 1 (amino acid residues 279-390) and a pro portion (residues 30-278) termed beta 1-latency-associated peptide (beta 1LAP). The dimeric form of beta 1LAP has been shown to associate noncovalently with the mature growth factor, resulting in inactivation of biological activity. To further characterize this interaction, the mature TGF beta 1 was radioiodinated and used to determine dissociation constants. A cross-linking method using the bifunctional covalent cross-linker bis-(sulfosuccinimidyl)suberate was found to be the best approach for measuring the amount of bound growth factor. The efficiency of cross-linking was constant within each experiment and varied between 45-55%. Saturation plots and their associated Scatchard analyses indicate apparent Kd values between 1.1-1.8 nM. Competition of TGF beta 1 binding to beta 1LAP by TGF beta 2 and TGF beta 3 (two closely related growth factors) revealed that the latter also bind beta 1LAP tightly, with apparent Kd values of 1.9 and 0.4 nM, respectively.

Triple helix formation by purine-rich oligonucleotides targeted to the human dihydrofolate reductase promoter

The ability of oligodeoxynucleotides to form specific triple helical structures with critical regulatory sequences in the human dihydrofolate reductase (DHFR) promoter was investigated. A battery of purine-rich oligonucleotides targeted to the two purine.pyrimidine strand biased regions near the DHFR transcription initiation site was developed. The stable triple helical structures formed by binding of the oligonucleotides to the native promoter double helix were dominated by G*G.C triplets, with interspersed C*C.G and A*A.T alignments. Mismatches between the oligonucleotide and the purine-rich strand of the target significantly destabilized third strand binding, and a G*A.T alignment was particularly unfavorable. Formation of a pur.pur.pyr triple helical structure results in a localized limitation of access to the native double helical DNA and produces sequence dependent conformational alterations extending several nucleotides beyond the triplex-duplex boundary. Although they differ only by the insertion of two A.T base pairs, the distal and proximal purine.pyrimidine regions can be targeted individually due to the high degree of sequence specificity of triple helical alignment. Triplex formation overlapping any of three consensus transcriptional regulatory elements and collectively covering 50% of the DHFR core promoter is now possible with this set of oligonucleotides.