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M K Smith

Publications and source records attributed to M K Smith.

At least 37 records · Page 2Linked to original sources
PubMed1998

A matrix-located processing peptidase of plant mitochondria.

Nuclear-encoded mitochondrial precursor proteins are proteolytically processed inside the mitochondrion after import. The general mitochondrial processing activity in plant mitochondria has been shown to be integrated into the cytochrome bc1 complex of the respiratory chain. Here we investigate the occurrence of an additional, matrix-located processing activity by incubation of the precursors of the soybean mitochondrial proteins, alternative oxidase, the FAd subunit of the ATP synthetase and the tobacco F1 beta subunit of the ATP synthase, with the membrane and soluble components of mitochondria isolated from soybean cotyledons and spinach leaves. A matrix-located peptidase specifically processed the precursors to the predicted mature form in a reaction which was sensitive to orthophenanthroline, a characteristic inhibitor of mitochondrial processing peptidase (MPP). The specificity of the matrix peptidase was illustrated by the inhibition of processing of the alternative oxidase precursor in both soybean and spinach matrix extracts upon altering a single amino acid residue in the targeting presequence (-2 Arg to Gly). Additionally, there was no evidence for general proteolysis of precursor proteins incubated with the matrix. The purity of the matrix fractions was ascertained by spectrophotometric and immunological analyses. The results demonstrate that there is a specific processing activity in the matrix of soybean and spinach in addition to the previously well characterized membrane-bound MPP integrated into the cytochrome bcl complex of the respiratory chain.

Cell Nucleus↗
PubMed1998

Co-operation between follicular ornithine decarboxylase and v-Ha-ras induces spontaneous papillomas and malignant conversion in transgenic skin.

Ornithine decarboxylase (ODC) is aberrantly regulated in tumor cells and results in high basal levels of ODC and polyamines in many epithelial tumors. To determine if elevated ODC/polyamine levels can co-operate with a mutant Ha-ras gene in mouse skin tumorigenesis, double transgenic mice were generated by breeding K6/ODC transgenic mice with TG.AC v-Ha-ras transgenic mice. A K6 keratin promoter drives the ODC transgene in K6/ ODC transgenic mice, which results in elevated ODC/ polyamine levels directed to the outer root sheath cells of hair follicles. TG.AC transgenic mice carry a v-Ha-ras transgene while still retaining two normal c-Ha-ras alleles. Transgenic mice that possess only the K6/ODC or the v-Ha-ras transgene did not develop tumors unless treated with either a carcinogen or a tumor promoter, respectively. However, a high percentage of double transgenic mice possessing both the K6/ODC and v-Ha-ras transgenes developed spontaneous tumors. All tumors were well-differentiated keratoacanthomas, some of which progressed to carcinomas within 2 months. The development and the maintenance of these ODC/ras tumors was ODC-dependent since alpha-difluoromethylornithine (DFMO), a specific ODC inhibitor, prevented the formation and caused the regression of these tumors. These findings indicate that ODC overexpression and an activated Ha-ras are sufficient to produce a high rate of malignant transformation in an animal model. The ODC/ras double transgenic mouse provides a simple in vivo model without the use of chemical carcinogens or tumor promoters in which to test downstream effectors that play a key role in mediating the development of epithelial tumors resulting from the cooperation between ODC and v-Ha-ras.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1997

Ornithine decarboxylase overexpression leads to increased epithelial tumor invasiveness.

Ornithine decarboxylase (ODC) overexpression cooperates with genetic lesions such as an activated c-rasHa to enhance epithelial tumorigenesis. To assess the invasiveness of ODC-overexpressing cells, two noninvasive epidermal cell lines, nontumorigenic BK-1 cells, and the papilloma-derived cell line SP-1 were infected with a replication-defective retrovirus that overexpresses ODC, inoculated into deepithelialized rat tracheas, and transplanted into athymic nude mice. After 5 weeks, ODC-overexpressing BK-1 cells remained localized on the luminal surface of the tracheal xenotransplants, whereas the ODC-overexpressing SP-1 cells were extremely invasive, with the whole tracheal wall penetrated. This invasiveness of ODC-overexpressing SP-1 cells was accompanied by elevated proteinase expression, including increased urokinase plasminogen activator activity in ODC-overexpressing cells and elevated stromelysin-1 mRNA expression in the stromal cells of invaded tracheal transplants.

Animals↗
PubMed1997

Application of plant and earthworm bioassays to evaluate remediation of a lead-contaminated soil.

Earthworm acute toxicity, plant seed germination/rootelongation (SG/RE) and plant genotoxicity bioassays were employed to evaluatethe remediation of a lead-contaminated soil. The remediation involved removalof heavy metals by a soil washing/soil leaching treatment process. A portionof the soil after remediation was rinsed with water in order to simulateexposure to rainfall. The bioassay results showed that the soils beforetreatment (BT) and after treatment plus water rinsing (RT) were not toxic toearthworms in a 14-day exposure, while after treatment (AT) showedsignificant toxicity. The LC50 values for Eisenia fetida andLumbricus terrestris were 44.04 and 28.83 (as % AT soilsupplemented in artificial soil), respectively. The phytotoxicity dataindicated that all three test soils significantly inhibited lettuce SG/RE ina dose-related manner, with AT being the most phytotoxic. In oats, RT had noeffect on SG/RE and AT was more toxic than BT. For the two local site grassseeds tested (blue grama and sideoat grama), the AT soil was the mostphytotoxic followed by BT and RT. In Allium cepa (common onion), BTand AT induced similar levels of genetic damage to root tip cells, whereas RTwas not genotoxic. High salt levels generated during the remediation processappeared to be responsible for the increased toxicity of AT soil for bothplants and earthworms. The rinsing of the AT soil with water effectivelyremoved both acutely toxic and genotoxic components of the soil.

Animals↗
PubMed1997

Differential expression of the multigene family encoding the soybean mitochondrial alternative oxidase.

The alternative oxidase (AOX) of the soybean (Glycine max L.) inner mitochondrial membrane is encoded by a multigene family (Aox) with three known members. Here, the Aox2 and Aox3 primary translation products, deduced for cDNA analysis, were found to be 38.1 and 36.4 Kd, respectively. Direct N-terminal sequencing of partially purified AOX from cotyledons demonstrates that the mature proteins are 31.8 and 31.6 KD, respectively, implying that processing occurs upon import of these proteins into the mitochondrion. Sequence comparisons show that the processing of plant AOX proteins occurs at a characteristic site and that the AOX2 and AOX3 proteins are more similar to one another than to other AOX proteins, including soybean AOX1. Transcript analysis using a polymerase chain reaction-based assay in conjunction with immunoblot experiments indicates that soybean Aox genes are differentially expressed in a tissue-dependent manner. Moreover, the relative abundance of both Aox2 transcripts and protein in cotyledons increase upon greening of dark-grown seedlings. These results comprehensively explain the multiple AOX-banding patterns observed on immunoblots of mitochondrial proteins isolated from various soybean tissues by matching protein bands with gene products.

Amino Acid Sequence↗
PubMed1997

Teaching cardiopulmonary resuscitation in a developing country: using Nicaragua as a model.

This article discusses the experience of teaching cardiopulmonary resuscitation (CPR) within a cross-cultural context. The purpose of the two CPR programs, to both the physicians and nurses at the Ministry of Health and the faculty at the UPOLI School of Nursing, were to "train the trainer" using these health professionals to become trainers in the area of CPR.

Cardiopulmonary Resuscitation↗
PubMed1997

When a physician harms a patient by a medical error: ethical, legal, and risk-management considerations.

Errors that harm patients are infrequently brought to the attention of these patients. The full disclosure of such medical errors is in the best interest of patients because it allows them to understand what has occurred, and to gain appropriate compensation for the harm that they have suffered. Physicians have been given little guidance regarding how to conduct a relationship with the patient after such an injury. We argue that the physician must continue to respect the patient, and communicate honestly with him or her throughout their relationship, even after the patient has been injured. It is painful to admit our errors, especially to those who have been harmed by them. Nevertheless, offering an apology for harming a patient should be considered to be one of the ethical responsibilities of the profession of medicine. Monetary compensation alone is not to be offered as a charitable gesture; rather, it should be accompanied by an apology to demonstrate the responsibility of the physician to the trusting patient. Full and honest disclosure of errors is most consistent with the mutual respect and trust patients expect from their physicians. Clearly, physicians' ethical responsibilities sometimes differ from their legal and risk-management responsibilities.

Adult↗
PubMed1996

Characterization of the import pathway of the F(A)d subunit of mitochondrial ATP synthase into isolated plant mitochondria.

The synthetic precursor of the F(A)d subunit of mitochondrial ATP synthase was imported into isolated soybean cotyledon mitochondria. Import of the F(A)d precursor was accompanied by processing to a lower molecular weight mature form. The F(A)d precursor displayed the following import characteristics not seen before with plant mitochondria: efficient import in the absence of external ATP and import of wheat germ-translated precursor. Pretreatment of the F(A)d precursor with NEM did not inhibit import. Taken together with the lack of a requirement for external ATP, this indicates that this precursor does not require extramitochondrial ATP-dependent factors for import. Binding studies indicated that the F(A)d precursor bound to a proteinaceous component of the mitochondrial outer membrane. Inhibitor studies indicated that processing was most likely via the general mitochondrial processing peptidase. The results suggest that import of this subunit occurs via a pathway different from the general import pathway described for the majority of precursor proteins.

Biological Transport, Active↗
PubMed1996

Evidence for a link between translocation and processing during protein import into soybean mitochondria.

The effect of metal chelators on protein import was investigated using isolated soybean mitochondria and soybean precursor proteins. Adding 1,10-phenanthroline, a metal chelator that can cross both mitochondrial membranes abolished import of both the alternative oxidase, and the F(A)d subunit of the ATP synthase, a matrix located protein. Other metal chelators such as EDTA, 1,7-phenanthroline and 4,7-phenanthroline, which cannot cross the mitochondrial membranes, had no effect on import. When processing, a known metal-dependent step inside mitochondria, was inhibited using a mutagenesis approach (changing a -2 arginine to a -2 glycine in the pre-piece of the precursor), so was import. Thus it would appear that in soybean, at least, translocation of proteins across the mitochondrial membrane, as well as processing, relies on a metal dependent step. Taken together, the data suggest the two processes may be directly connected in these mitochondria.

Amino Acid Sequence↗
PubMed1996

Developmental effects of trichloroacetonitrile administered in corn oil to pregnant Long-Evans rats.

Trichloroacetonitrile (TCAN) is a by-product of the chlorine disinfection of water containing natural organic material. When administered by gavage to pregnant Long-Evans rats in a medium-chain triglyceride vehicle, tricaprylin oil (Tricap), at a volume of 10 ml/kg, TCAN induced fetal cardiovascular anomalies at doses as low as 1 mg/kg/d (Smith et al., 1988). A slight but possibly biologically significant increase over the water control group in adverse pregnancy outcomes (resorptions, reduced fetal weight, and anomalies) was observed in the Tricap control group. This led us to reexamine the development effects of TCAN in a second vehicle, corn oil (CO). Five groups of approximately 20 pregnant female rats received TCAN in CO at 15, 35, 55, and 75 mg/kg/d, and in Tricap at 15 mg/kg/d (10 ml/kg dosing volume). Corn oil, Tricap, and water served as vehicle controls. Animals were treated by oral intubation on gestation d 6-18 (vaginal plug = d 0). Five out of 20 dams (75 mg/kg) died during treatment. Adjusted maternal weight gain was lower in females receiving 35 mg/kg TCAN or greater. The mean percent of nonlive implants per litter was elevated at 55 and 75 mg/kg TCAN (CO). The TCAN dose-response curve for fetal (but not maternal) effects was shifted to the right when CO was compared to Tricap. Fetal weight was reduced at 15 mg/kg TCAN (Tricap) and at > or = 55 mg/kg TCAN (CO). When TCAN was administered in CO, the mean frequency of soft-tissue malformations decreased with significantly fewer septal and great vessel cardiovascular defects observed. We hypothesize that the volatile haloacetonitrile, TCAN, may interact with the Tricap vehicle in such a way that effects on the developing cardiovascular system are potentiated. The lowest observed adverse effect level for TCAN (CO) was determined to be 35 kg/kg.

Acetonitriles↗
PubMed1996

Spontaneous and posed facial expression in Parkinson's disease.

Spontaneous and posed emotional facial expressions in individuals with Parkinson's disease (PD, n = 12) were compared with those of healthy age-matched controls (n = 12). The intensity and amount of facial expression in PD patients were expected to be reduced for spontaneous but not posed expressions. Emotional stimuli were video clips selected from films, 2-5 min in duration, designed to elicit feelings of happiness, sadness, fear, disgust, or anger. Facial movements were coded using Ekman and Friesen's (1978) Facial Action Coding System (FACS). In addition, participants rated their emotional experience on 9-point Likert scales. The PD group showed significantly less overall facial reactivity than did controls when viewing the films. The predicted Group X Condition (spontaneous vs. posed) interaction effect on smile intensity was found when PD participants with more severe disease were compared with those with milder disease and with controls. In contrast, ratings of emotional experience were similar for both groups. Depression was positively associated with emotion rating but not with measures of facial activity. Spontaneous facial expression appears to be selectively affected in PD, whereas posed expression and emotional experience remain relatively intact.

Aged↗
PubMed1995

Implementing annual cancer screenings for elderly women.

1. Secondary prevention, in the form of regular screenings, is the most effective approach to early detection of breast and cervical cancer. 2. Women over 50 years of age are at increased risk for breast and cervical cancer, yet a disproportionate number of these women do not receive screening for breast and cervical cancer. 3. A protocol, in the form of a flowchart, can be used as an assessment tool to determine a client's status, needs, progress, and direction for future health care.

Aged↗
PubMed1994

Isolation of a novel soybean gene encoding a mitochondrial ATP synthase subunit.

A novel ATP synthase gene from soybean has been cloned and characterized. A subunit from the FA portion of the complex is encoded by two nuclear genes. The genomic clone(s) contain five exons encoding a protein of 179 amino acids. The amino terminal end contains many properties of a mitochondrial targeting sequence and preliminary in vitro import studies indicate that there is a cleavable precursor of approximately 30 amino acids. The predicted protein sequence shows high homology with the N-terminal sequence from an isolated subunit of ATP synthase complex from spinach (Hamsaur and Glaser (1992) Eur. J. Biochem. 205, 409-416). The subunit was tentatively identified as the equivalent of subunit d in bovine and P18 in yeast based on structural identity.

Amino Acid Sequence↗
PubMed1994

Subcortical contributions to head movements in macaques. II. Connections of a medial pontomedullary head-movement region.

1. In the companion article, a variety of head movements were elicited by stimulation in, and adjacent to, the gigantocellular reticular nucleus (Cowie and Robinson 1994). We refer to this area, caudal to the abducens nucleus, as the gigantocellular head movement region. In the present paper, the anatomical connections of this region, as determined by injections of wheat-germ agglutinin conjugated horseradish peroxidase (WGA-HRP), are reported. The majority of efferent and afferent connections were with areas related to head movements. 2. Efferent fibers from the region projected via two paths to the caudal medulla and upper cervical spinal cord. Labeled fibers descended in the anterolateral funiculus of the ipsilateral spinal cord to terminate in lateral parts of the ventral horn. A second pathway descended bilaterally in the medial longitudinal fasciculus to the anterior funiculi and medial portions of the ventral gray. These efferents paralleled the head-movement topography demonstrated physiologically. Other projections included efferents to the interstitial nucleus of Cajal, caudal field H of Forel, paramedian pontine reticular formation, and caudal vestibular nuclei. Other efferent fibers projected to the trigeminal, facial, and hypoglossal nuclei, as well as to the parvocellular reticular field, which contains interneurons for these motor groups. However, no efferent or afferent labeling involved the ocular motor nuclei. 3. Afferents to the gigantocellular head movement region arose mainly from head-movement areas. In all animals, labeled cells were found in the intermediate and deep layers of the caudal superior colliculus. Labeled neurons also were found in the caudal field H of Forel, interstitial nucleus of Cajal, pontine medial tegmentum including the pontine paramedian reticular formation, nucleus subcoeruleus, and vestibular nuclear complex. Caudally, filled cells were located in the parvocellular, magnocellular, dorsal, and ventral reticular nuclei, the supraspinal nucleus, and the upper cervical ventral horn. 4. In one animal, the ipsilateral frontal cortex contained retrogradely labeled neurons. These cells were found in layer V of cortical areas 4 and 6. Other afferent cells were found consistently in the periventricular and periaqueductal gray matter. 5. A control injection into the caudal vestibular nuclear complex showed projections to the gigantocellular reticular formation and labeled cells in the vestibular and parvocellular reticular nuclei. These observations show that the connections of the gigantocellular region are not typical of all head movement sites. 6. These data indicate that the gigantocellular head-movement region has the requisite efferent and afferent connections to function in the subcortical control of head, but not eye, movements.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Informed consent and medical ethics.

Informed consent is based on a shared decision between physician and patient, with the physician understanding the relevant values of the patient and the patient understanding the nature of the disease and intervention, including risks and benefits. Informed consent has developed rapidly since it was introduced in the 1950s, reflecting recent changes in the practice of medicine that respect the increase of patient autonomy. The purpose of the written consent form is to document that a process of informed consent has taken place. It is generally agreed that all surgical as well as research procedures require written consent. For certain nonsurgical procedures, the decision regarding obtaining written consent will consider both the risk involved for the patient and the general community standard. Informed consent serves as an important symbol of a physician-patient relationship that adheres to the valued principles of medical ethics.

Consent Forms↗
PubMed1993

Perinatal toxicity associated with nickel chloride exposure.

Several reports have suggested that soluble nickel salts may affect development. In this study female Long-Evans rats drank nickel chloride solutions (0, 10, 50, or 250 ppm Ni) for 11 weeks prior to mating and then during two successive gestation (G1, G2) and lactation (L1, L2) periods. Pups were observed until weaning; breeder males were unexposed. Dams drinking 250 ppm consumed less liquid and more food per kilogram body weight than did controls (liquid: prebreeding, G1, and G2; food: prebreeding, G2 and L2). Maternal weight gain was reduced during G1 in the high- and middle-dose groups; indices of reproductive performance were comparable across groups. Pup birth weight was unaltered by treatment and weight gain was reduced only in male pups exposed to 50 ppm Ni during L1. The frequency of perinatal death is the most significant toxicologic finding of the study. The proportion of dead pups per litter was significantly elevated at the high dose in L1 and at 10 and 250 ppm in L2 (50 ppm, P = 0.076), with a dose-related response in both experimental segments. The number of dead pups per litter was significantly increased at each dose in L2. Prolactin levels in pups were unchanged by treatment and were reduced in dams at the high dose. We conclude that 10 ppm Ni represents the lowest observed adverse effect level (LOAEL) in this study.

Animals↗