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Biomedical subjects

L Dixon

Publications and source records attributed to L Dixon.

At least 19 recordsLinked to original sources
PubMed1992

Magnetic resonance imaging evaluation helps to delineate a recurrent skin cancer present under the skin flap.

A case of recurrent squamous cell carcinoma under a skin flap as confirmed and delineated by magnetic resonance imaging (MRI) is described. This report illustrates a potentially new indication for MRI in clinical dermatology, namely, to define skin cancer recurrences under skin flaps and grafts and to determine the extent of underlying tissue involvement. The cost-effectiveness of MRI and the use of gadolinium, an MRI contrast agent, in the evaluation of skin tumors are also addressed.

Aged↗
PubMed1991

The sequences of the ribonucleotide reductase genes from African swine fever virus show considerable homology with those of the orthopoxvirus, vaccinia virus.

Two African swine fever virus (ASFV) recombinant plasmids containing large inserts of DNA have been sequenced at random, and translations of the DNA sequence have been compared to libraries of vaccinia virus protein sequences. Among other genes identified by their extensive homology with vaccinia virus genes were the large and small subunits of ribonucleotide reductase. A 5.5-kb fragment from the Malawi (LIL20/1) strain of ASFV was identified as containing the genes for both these subunits. The fragment has been sequenced and the two genes have been found to be in a head-to-head orientation. The sequences are compared to other sequenced ribonucleotide reductase genes, and the evolutionary implications discussed.

African Swine Fever Virus↗
PubMed1991

Drug abuse in schizophrenic patients: clinical correlates and reasons for use.

OBJECTIVE: This study aimed to 1) determine substance abuse prevalence and preference in a diverse sample of schizophrenic, schizoaffective, and schizophreniform inpatients, 2) compare drug-abusing and non-drug-abusing patients on demographic and clinical variables during the acute and stabilization phases of their hospital course, and 3) obtain data from patients on reasons for drug abuse and on acute state-related changes during periods of intoxication. METHOD: Eighty-three psychotic inpatients consecutively admitted to a New York City teaching hospital were evaluated. Sixty-eight had schizophrenia, 12 had schizoaffective disorder, and three had schizophreniform disorder diagnosed according to the Structured Clinical Interview for DSM-III-R. Each patient received ratings on the Brief Psychiatric Rating Scale, the Global Assessment Scale, and the Scale for the Assessment of Negative Symptoms at admission and at discharge, an evaluation of premorbid adjustment, and an extensive interview on drug and alcohol use. RESULTS: Forty (48%) of the patients received diagnoses of drug or alcohol abuse or dependence. The drug-abusing patients primarily used cannabis (N = 26), alcohol (N = 21), and cocaine (N = 14) and reported that they abused drugs to get "high," to relieve depression, and to relax. They had significantly fewer positive and negative symptoms at discharge, better sexual adjustment and worse school performance during adolescence, and more family histories of drug abuse than the non-drug-abusing patients. CONCLUSIONS: Schizophrenic patients who abuse drugs may represent a subgroup of patients with better prognoses and less severe clinical characteristics of schizophrenia, but their drug abuse may adversely affect global outcome.

Adolescent↗
PubMed1990

Acute effects of drug abuse in schizophrenic patients: clinical observations and patients' self-reports.

Substance abuse among schizophrenic patients is an increasingly recognized clinical phenomenon. The authors review experimental and observed clinical effects of drug abuse and patients' subjective experiences of acute intoxication. Though drug abuse may exacerbate psychotic symptoms, abused drugs may also lead to transient symptom reduction in subgroups of schizophrenic patients. Some patients report feeling less dysphoric, less anxious, and more energetic while intoxicated. Models of the relationship of drug abuse and schizophrenia, particularly the self-medication hypothesis, are discussed in reference to these data.

Humans↗
PubMed1989

Intake of greasy diets in hypothalamic obesity: a re-assessment.

Rats with medial hypothalamic lesions are known to prefer greasy diets. Past research has suggested that this is based on the oily texture rather than caloric content of these foods. We have re-examined this appetite in rats with bilateral parasagittal knife-cuts between the medial and lateral hypothalamus. Following knife cuts vs. sham surgery, the body weight and food consumption of adult female rats were monitored during four experimental phases. During the first month post-surgery rats were fed powdered Chow (3.61 kcal/g) and showed the usual hyperphagia and obesity. Each group was then subdivided and fed either a high-fat diet (5.5 kcal/g) or a similarly greasy mineral-oil diet (3.61 kcal/g) for a second month. The knife-cut group fed high-fat showed significantly higher intake than both sham-cut controls and knife-cut rats fed the mineral-oil diet. The latter group showed only a non-significant feeding increase over controls. Following a third month when all groups again received Chow, animals were given the opposite greasy diet for a final month. Knife-cut rats previously fed the high-fat diet showed significant overeating of the mineral-oil diet and defended their obesity, while those fed the mineral-oil free diet first now showed significant hyperphagia and obesity on the high-fat diet. Across both target phases (months 2 and 4) knife-cut rats always ate significantly more of the high-fat diet than of the mineral-oil diet. The latter only elicited hyperphagia in animals that had been previously exposed to the high-fat diet. These findings suggest that the hyperphagic response to greasy foods relatively low in calories and digestible fats by rats with hypothalamic injury is a function of prior experience with the sensory and/or metabolic consequences of having first eaten highly caloric fatty foods. If that is true, it may be that such animals are capable of learning positive food-associated cues in addition to negative ones (i.e. enhanced taste aversions) documented earlier by other investigators.

Animals↗
PubMed1989

Management of neuroleptic-induced movement disorders: effects of physician training.

Residents given a specialized 4-hour course in managing extrapyramidal syndromes prescribed significantly lower neuroleptic doses and were more skilled at diagnosis of extrapyramidal syndromes than residents given standard psychopharmacology training. The results suggest that focused training in extrapyramidal syndromes should be part of residency curricula.

Antipsychotic Agents↗
PubMed1989

Variations in the perceived need for orthodontic treatment in a sample of 14-year-old children in North Derbyshire.

The investigation explored the possibility that failure to present for orthodontic treatment might result from failure by the child or parent to recognise the existence of an irregular dentition, or to perceive an irregular dentition as a cause for concern. Although a previous investigation by the present authors revealed that a substantial number of the 14-year-old children who had not received and were not scheduled for treatment were in need of orthodontic intervention, use of the SCAN index showed that the great majority did not perceive themselves as having a markedly unattractive dental appearance. Furthermore, almost 86 per cent of the children who had not received and were not scheduled for orthodontic treatment declared themselves happy with their dental aesthetics, as did a similar proportion of their parents. On the other hand, a large majority of children scheduled for orthodontic treatment, together with their parents, reported themselves unhappy with the dental aesthetics.

Adolescent↗
PubMed1989

The orthodontic condition and treatment status of a sample of 14-year-old children in North Derbyshire.

In conjunction with a survey of the general dental health of 14-year-old children in North Derbyshire, an investigation was undertaken into their orthodontic condition and treatment status. It was found that approximately 60 per cent of children had not already received and were not scheduled for orthodontic treatment, but that many of these had abnormalities warranting orthodontic intervention. Girls were more likely than boys to receive orthodontic treatment, but children of socio-economic classes 1, 2 and 3N were not significantly more likely to receive treatment than were children of socio-economic classes 3M, 4 and 5.

Adolescent↗
PubMed1987

Endocrine changes in the late-follicular and postovulatory intervals as determinants of the in vitro fertilization pregnancy rate.

This investigation examines the hormone pattern in in vitro fertilization (IVF) cycles from the time of human chorionic gonadotropin (hCG) administration through embryo transfer to ascertain whether the absolute levels or secretory patterns of the major reproductive hormones affect the IVF pregnancy rate. Thirty-one women who underwent IVF treatment were enrolled in the study. All patients received clomiphene citrate/human menopausal gonadotropin for ovulation induction. Significant elevations in serum estradiol (E2) levels in the pregnant group were found throughout the cycle interval studied. After hCG administration the serum hCG levels were not different between the groups. Significant elevations in serum progesterone (P) concentrations were found in the pregnant group from the day after laparoscopy through embryo transfer. Embryos obtained from the pregnant group appeared to be different in that the mean number of blastomeres per embryo transferred was significantly greater. Therefore for achievement of an IVF pregnancy the optimal hormone pattern employing combination ovulation induction in the ovulation to transfer interval is a relatively high E2 level in ovulation followed by a high P level at transfer and into the luteal phase. These elevated hormone levels do not depend on the response to exogenous hCG.

Adult↗
PubMed1986

Oligonucleotide directed mutagenesis of cauliflower mosaic virus DNA using a repair-resistant nucleoside analogue: identification of an agnogene initiation codon.

Mutation of the initiation codon of the dispensible open reading frame, ORF VII, of cauliflower mosaic virus (CaMV) delayed the appearance of disease symptoms, but the mutants reverted with high frequency. This suggests a role of this start codon in viral expression. Oligonucleotide-directed mutagenesis, utilizing a novel, repair-resistant deoxyguanosine analogue, 2'-deoxy-7-deazainosine (dDI), highly improved the yield of mutants.

Base Sequence↗
PubMed1985

HLA class II regulation and structure. Analysis with HLA-DR3 and HLA-DP point mutants.

Point mutations that affect HLA-DR structure or expression have not previously been described. In the present study, we isolated such mutants by immunoselection of an ethyl methanesulfonate-mutagenized HLA-DR3 cell line with an anti-HLA-DR3 monoclonal antibody, 16.23. To facilitate analysis, we used a parent cell line with a preexisting deletion of one haplotype encompassing DR and DQ alpha and beta. The selection yielded two sets of mutants, one with defects in DR3 structure, the other with defects in different steps leading to DR expression. Of the expression-defective mutants, one had undergone a second deletion removing the remaining DR alpha gene but no other class II genes. It had a normal abundance of DR beta mRNA but had lost binding of DR monomorphic antibodies, indicating that DR beta chains do not form noncognate dimers. A second mutant had an abnormally large DR alpha mRNA, probably resulting from a splice site mutation. Several mutants had marked reductions in DR beta mRNA levels; in two of these, the lesion appeared to be transcriptional because the reduction in DR beta mRNA was paralleled by an altered methylation pattern of one of the DR beta genes. Other expression-defective mutants had different posttranscriptional defects. Some of the mutations were similar to those that have been found in mouse strains defective in I-E expression, whereas others have no known natural counterpart. The matrix of reactivities of anti-HLA class II monomorphic antibodies with these and similar mutants allowed us to define the gene products recognized by these antibodies. A set of seven mutants were "epitope defective," that is, they expressed normal or near normal levels of HLA-DR3 but no longer bound 16.23. Unexpectedly, each of the epitope mutants had decreased DR dimer stability. These mutants should be useful in localizing the DR3 alloepitope and in elucidating its contribution as a restriction element in the presentation of soluble antigen to immune T cells.

Antibodies, Monoclonal↗
PubMed1975

Localization of spherocytosis to chromosome 8 or 12 and report of a family with spherocytosis and a reciprocal translocation.

Significant linkage was found between spherocytosis and a translocation involving the short arms of chromosomes 8 and 12. The gene for spherocytosis, therefore, is likely either very close to the centromere of chromosome 8 or on 12p. The unusually high frequency of spontaneous abortion in this family was probably due to this translocation and was unrelated to the spherocytosis.

Adult↗