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Biomedical subjects

J D Evans

Publications and source records attributed to J D Evans.

At least 55 records · Page 3Linked to original sources
PubMed1999

Differential gene expression between developing queens and workers in the honey bee, Apis mellifera.

Many insects show polyphenisms, or alternative morphologies, which are based on differential gene expression rather than genetic polymorphism. Queens and workers are alternative forms of the adult female honey bee and represent one of the best known examples of insect polyphenism. Hormonal regulation of caste determination in honey bees has been studied in detail, but little is known about the proximate molecular mechanisms underlying this process, or any other such polyphenism. We report the success of a molecular-genetic approach for studying queen- and worker-specific gene expression in the development of the honey bee (Apis mellifera). Numerous genes appear to be differentially expressed between the two castes. Seven differentially expressed loci described here belong to at least five distinctly different evolutionary and functional groups. Two are particularly promising as potential regulators of caste differentiation. One is homologous to a widespread class of proteins that bind lipids and other hydrophobic ligands, including retinoic acid. The second locus shows sequence similarity to a DNA-binding domain in the Ets family of transcription factors. The remaining loci appear to be involved with downstream changes inherent to queen- or worker-specific developmental pathways. Caste determination in honey bees is typically thought of as primarily queen determination; our results make it clear that the process involves specific activation of genes in workers as well as in queens.

Animals↗
PubMed1999

Complete nucleotide sequence of a cryptic plasmid from the ruminal bacterium Selenomonas ruminantium HD4 and identification of two predicted open reading frames.

A cryptic plasmid (pSR1) isolated from Selenomonas ruminantium HD4 was previously cloned into the HindIII site of pBR322 and a restriction map was constructed using HindIII, ClaI, BamHI, and PvuII (S. A. Martin and R. G. Dean, Appl. Environ. Microbiol. 55(12), 3035-3038, 1989). Analysis of the nucleotide sequence of pSR1 revealed two major open reading frames (ORFs) located in the minus strand at different frames. Analysis of ORF-1 revealed that it has 325 amino acids with a predicted MW of 36,588, and ORF-2 has 379 amino acids with a predicted MW of 42,651. The ORF-1 amino acids showed 30 to 32% sequence homology to the hypothetical protein YtqA in Bacillus subtilis and another hypothetical protein in the thermophilic bacterium Aquifex aeolicus. ORF-2 showed limited homology (23%) to the hypothetical protein ICFG in the photosynthetic cyanobacteria Synechocystis PCC6803.

Amino Acid Sequence↗
PubMed1999

Cognitive deficits and psychopathology in institutionalized versus community-dwelling elderly schizophrenia patients.

We evaluated psychiatric symptoms and neurocognitive functioning among 25 institutionalized and 25 outpatient DSM-IV-diagnosed schizophrenia patients, as well as 25 middle-aged and elderly normal comparison subjects. All subjects were assessed with the Positive and Negative Syndrome Scale, Hamilton Rating Scale for Depression, modified Simpson-Angus Extrapyramidal Symptom Scale, the Abnormal Involuntary Movement Scale, and the Mattis Dementia Rating Scale (DRS). The two patient groups had similar levels of depressive symptoms, but the institutionalized patients had more severe positive and negative symptoms and were on higher doses of neuroleptic medication. The institutionalized patients had significantly more cognitive impairment on the DRS than outpatients and normal comparison subjects, particularly on the subscales of initiation/perseveration, conceptualization, and memory. Results are discussed in terms of the possible neuropathology associated with cognitive impairment in chronic schizophrenia.

Aged↗
PubMed1999

Norms for letter and category fluency: demographic corrections for age, education, and ethnicity.

Letter and category fluency tasks are used to assess semantic knowledge, retrieval ability, and executive functioning. They appear to be useful in detecting different types of dementia, but accurate detection of neuropsychological impairment relies on appropriate normative data. Multiple regression analysis was used to develop demographically corrected norms for letter and category fluency in 768 normal adults. T-score equations were developed on a base subsample of 403, and crossvalidated on a separate subsample (n = 365). Participants ranged in age from 20 years to 101 years; in educational level from 0 to 20 years; 55% were Caucasian and 45% were African American. Together, age, education, and ethnicity were significant predictors of letter and category fluency performance, accounting for 15% and 25% of variance, respectively. Formulas and tables for converting raw fluency scores to demographically corrected T scores are presented.

Adult↗
PubMed1999

Schizoaffective disorder: a form of schizophrenia or affective disorder?

BACKGROUND: The diagnostic status of schizoaffective disorder continues to be controversial. Researchers have proposed that schizoaffective disorder represents a variant of schizophrenia or affective disorder, a combination of the 2, or an intermediate condition along a continuum between schizophrenia and affective disorder. METHOD: We compared outpatients aged 45 to 77 years with DSM-III-R diagnosis of schizoaffective disorder (N = 29), schizophrenia (N = 154), or nonpsychotic mood disorder (N = 27) on standardized rating scales of psychopathology and a comprehensive neuropsychological test battery. A discriminant function analysis was used to classify the schizoaffective patients based on their neuropsychological profiles as being similar either to schizophrenia patients or to those with nonpsychotic mood disorder. RESULTS: The schizoaffective and schizophrenia patients had more severe dyskinesia, had a weaker family history of mood disorder, had been hospitalized for psychiatric reasons more frequently, were more likely to be prescribed neuroleptic and anticholinergic medication, and had somewhat less severe depressive symptoms than the mood disorder patients. The schizophrenia patients had more severe positive symptoms than the schizoaffective and mood disorder patients. The neuropsychological performances of the 2 psychosis groups were more impaired than those of the nonpsychotic mood disorder patients. Finally, on the basis of a discriminant function analysis, the schizoaffective patients were more likely to be classified as having schizophrenia than a mood disorder. CONCLUSION: These findings suggest that schizoaffective disorder may represent a variant of schizophrenia in clinical symptom profiles and cognitive impairment.

Aged↗
PubMed1998

Correlates of functional status in older patients with schizophrenia.

There is a growing recognition of the importance of quantifying the impact of illness on functional abilities. Measures of function frequently rely on a self-report. Few studies have directly assessed functional capacity in psychiatric patients, especially older ones who may be at an increased risk for disability. Subjects were 102 middle-aged and elderly outpatients with DSM-III-R or DSM-IV diagnosis of schizophrenia or schizoaffective disorder, and 66 normal comparison subjects, ranging in age from 45 to 86. The Direct Assessment of Functional Status (DAFS), a standardized measure of behavior during simulated daily activity tasks (i.e. time orientation, communication, transportation, finance, shopping, grooming and eating) was used to quantify levels of disability. Schizophrenic patients demonstrated significantly greater disability than normal subjects. An evaluation of specific behaviors indicated that the patients were significantly more limited than comparison subjects across all subscales of the DAFS except for grooming and eating. A lower level of formal education, greater severity of extrapyramidal symptoms, and greater cognitive deficits, but not severity of symptoms of schizophrenia, were related to lower DAFS scores. Relative to published findings, schizophrenic patients appeared more disabled than outpatients with major depression, but less disabled than those with Alzheimer's disease. The DAFS is a useful instrument for characterizing functional abilities in older patients with schizophrenia. Our findings of significant functional disability in older schizophrenic patients have implications for treatment as well as allocation of health-care resources.

Activities of Daily Living↗
PubMed1998

Analytical solutions to a tapering multicylinder somatic shunt cable model for passive neurones.

A multicylinder somatic shunt cable model for passive neurones is considered in which one or more tapering equivalent cylinders emanate from a uniformly polarized soma. Each tapering equivalent cylinder approximates the loss of dendritic trunk parameter in the one or more dendritic trees that it represents, relaxing certain symmetry conditions necessary for the Rall equivalent cylinder concept and in particular allowing terminal branches to end at different electrotonic lengths. The case of exponential taper is considered in detail following the anatomical data on apical and basilar dendrites of CA1 and CA3 hippocampal pyramidal neurons obtained by Turner and Schwartzkroin [J. Neurophysiol. 44 (1980) 184; J. Neurosci. 3 (1983) 2381].

Dendrites↗
PubMed1997

Serum levels of insulin-like growth factors (IGF-I and IGF-II) and their binding protein (IGFBP-3) are not elevated in pancreatic cancer.

CONCLUSION: Serum levels of IGF-I, IGF-II, and IGFBP-3 are not elevated in pancreatic cancer and do not appear to have a significant role in glucose homeostasis in this group of patients. BACKGROUND: The insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) have been implicated recently in the pathogenesis of pancreatic cancer, and increased serum levels of IGF-I or IGF-II have been reported previously in a number of other gastrointestinal malignancies. METHODS: Serum levels of IGF-I, IGF-II, and IGFBP-3 were measured by RIA in 20 patients with pancreatic cancer and 20 age-matched healthy control subjects and correlated with serum glucose, C-peptide, and glucose tolerance. RESULTS: No significant difference was observed in serum levels of IGF-I (13 vs 17 nmol/L, respectively), IGF-II (0.67 vs 0.91 U/mL), or IGFBP-3 (2.3 vs 2.3 mg/L) between the two groups of patients. Twelve (60%) patients had impaired glucose tolerance, but no correlation was observed between the serum levels of the IGFs and glucose tolerance.

Aged↗
PubMed1997

Factors affecting lactate and malate utilization by Selenomonas ruminantium.

Lactate utilization by Selenomonas ruminantium is stimulated in the presence of malate. Because little information is available describing lactate-plus-malate utilization by this organism, the objective of this study was to evaluate factors affecting utilization of these two organic acids by two strains of S. ruminantium. When S. ruminantium HD4 and H18 were grown in batch culture on DL-lactate and DL-malate, both strains coutilized both organic acids for the initial 20 to 24 h of incubation and acetate, propionate, and succinate accumulated. However, when malate and succinate concentrations reached 7 mM, malate utilization ceased, and with strain H18, there was a complete cessation of DL-lactate utilization. Malate utilization by both strains was also inhibited in the presence of glucose. S. ruminantium HD4 was unable to grow on 6 mM DL-lactate at extracellular pH 5.5 in continuous culture (dilution rate, 0.05 h-1) and washed out of the culture vessel. Addition of 8 mM DL-malate to the medium prevented washout on 6 mM DL-lactate at pH 5.5 and resulted in succinate accumulation. Addition of malate also increased bacterial protein, acetate, and propionate concentrations in continuous culture. These results suggest that 8 mM DL-malate enhances the ability of strain HD4 to grow on 6 mM DL-lactate at extracellular pH 5.5.

Animals↗
PubMed1997

Chronic pancreatitis and pancreatic carcinoma.

The differential diagnosis between pancreatic cancer and chronic pancreatitis is very important as the management and prognosis of these two diseases is different. In most patients with pancreatic disease, the diagnosis can be established but there is a subgroup of patients in whom it is difficult to differentiate between these conditions because the clinical presentation is often similar and currently available diagnostic tests may be unable to distinguish between an inflammatory or neoplastic pancreatic mass. This paper reviews the aetiology, pathology and clinical features of these diseases and discusses the limitations of conventional diagnostic methods and how newer techniques may be of value in the differential diagnosis.

Chronic Disease↗
PubMed1997

Role of matrix metalloproteinases and their inhibitors in pancreatic cancer.

BACKGROUND/AIMS: The matrix metalloproteinases are a family of proteolytic enzymes which normally have an important physiological role in tissue remodelling and wound healing, but more recently have been implicated in the proteolytic events which occur during tumour invasion. METHODS: The expanding family of matrix metalloproteinases and the specific tissue inhibitors of the matrix metalloproteinases are reviewed including their classification, structure, function, regulation of activity, and tissue expression with particular reference to pancreatic cancer. The effect of synthetic matrix metalloproteinases inhibitors in preclinical studies is reviewed together with the results of ongoing clinical trials in pancreatic cancer. RESULTS: Pancreatic cancer is associated with the overexpression of several matrix metalloproteinases with a reduced expression of their specific inhibitors. Orally bioavailable matrix metalloproteinase inhibitors have successfully completed phase I/II clinical trials with promising results. Multicentre randomised controlled phase IIb/III clinical trials aren currently under way in pancreatic cancer. CONCLUSIONS: Matrix metalloproteinase inhibition may represent a novel approach to the management of pancreatic cancer not only in advanced disease, but in the adjuvant treatment setting following tumour resection either alone or in combination with existing chemotherapeutic agents.

Clinical Trials as Topic↗
PubMed1997

Outcome of surgery for chronic pancreatitis.

BACKGROUND: In patients with chronic pancreatitis, surgery is indicated for the management of intractable pain or for the treatment of complications. METHODS: Sixty-three consecutive patients (49 men and 14 women of median age 40 (range 20-72) years) who had undergone surgery over an 8-year interval for chronic pancreatitis were studied. The mortality and morbidity rates associated with surgery were assessed and quality of life was reviewed based on relief of symptoms, analgesic use, employment and long-term sequelae. RESULTS: Forty-four patients (70 per cent) had alcoholic chronic pancreatitis. In 60 patients the principal indication for surgery was intractable pain. Eighteen patients had a duodenum-preserving resection of the pancreatic head (Beger operation); the other surgical procedures were Whipple resection (15), left-sided resection (13), total pancreatectomy (seven), pseudocystjejunostomy (five), pancreaticojejunostomy (one) and bypass procedures (four). The median inpatient stay was 12 days; 23 patients had postoperative complications including one death (2 per cent). There was improved pain control (P < 0.001), a reduction in opiate analgesia use, increase in percentage weight gain (P < 0.01 at 2 years) and return to employment following surgery. Although there was an increase in diabetes mellitus and need for enzyme supplementation these were easily controlled. CONCLUSION: Surgery is an effective treatment in carefully selected patients with chronic pancreatitis but must be tailored to the pattern of disease in each individual.

Adult↗
PubMed1996

Duodenal gangliocytic paraganglioma presenting as an ampullary tumor.

CONCLUSION: We report a case of a duodenal gangliocytic paraganglioma that had an unusual clinical presentation and atypical immunohistochemical features. BACKGROUND: Duodenal gangliocytic paragangliomas are rare tumors of the gastrointestinal tract with approx 70 cases reported in the literature. The most common presentation is with gastrointestinal bleeding, whereas obstructive jaundice is very uncommon. Immunohistochemistry typically shows positive epithelial cell staining for somatostatin, pancreatic polypeptide, and other neuroendocrine markers. METHODS: A 56-yr-old man presented with intermittent episodes of epigastric pain, vomiting, and obstructive jaundice. Upper gastrointestinal endoscopy revealed a pedunculated ampullary tumor that was subsequently confirmed by computed tomography. At operation, there was marked secondary obstructive chronic pancreatitis in the remaining pancreas necessitating a pylorus-preserving total pancreatectomy. RESULTS: Histology confirmed typical features of a duodenal gangliocytic paraganglioma, but immunohistochemistry demonstrated negative staining for somatostatin and other polypeptides, which is in contrast to most other reported cases. Two years after surgery, the patient remains alive and well on medical treatment with no evidence of recurrent tumor.

Ampulla of Vater↗
PubMed1996

A clinical and neuropsychological comparison of delusional disorder and schizophrenia.

The authors evaluated 14 middle-aged and elderly patients with delusional disorder (DD) and 253 patients with schizophrenia (SC); all patients met DSM-III-R criteria. Because the DD patients were older and had a later age at onset of illness, a sub-sample of 50 SC patients with illness onset after age 40 was compared with the 14 DD patients on clinical and neuropsychological characteristics. The DD group had a less frequent history of past hospitalization but more severe overall psychopathologic symptoms. Level of neuropsychological impairment seemed somewhat lower in the DD group, but differences were nonsignificant because of small sample size. Diagnoses remained stable during up to 8 years' follow-up (average 4 years). These preliminary findings provide partial support to the clinical categorization of DD as a disorder distinct from SC.

Age of Onset↗
PubMed1995

Relatedness threshold for the production of female sexuals in colonies of a polygynous ant, Myrmica tahoensis, as revealed by microsatellite DNA analysis.

The genetic relationships of colony members in the ant Myrmica tahoensis were determined on the basis of highly polymorphic microsatellite DNA loci. These analyses show that colonies fall into one of two classes. In roughly half of the sampled colonies, workers and female offspring appear to be full sisters. The remaining colonies contain offspring produced by two or more queens. Colonies that produce female sexuals are always composed of highly related females, while colonies that produce males often show low levels of nestmate relatedness. These results support theoretical predictions that workers should skew sex allocation in response to relatedness asymmetries found within colonies. The existence of a relatedness threshold below which female sexuals are not produced suggests a possible mechanism for worker perception of relatedness. Two results indicate that workers use genetic cues, not queen number, in making sex-allocation decisions. (i) The number of queens in a colony was not significantly correlated with either the level of relatedness asymmetry or the sex ratio. (ii) Sex-ratio shifts consistent with a genetically based mechanism of relatedness assessment were seen in an experiment involving transfers of larvae among unrelated nests. Thus workers appear to make sex-allocation decisions on the basis of larval cues and appear to be able to adjust sex ratios long after egg laying.

Alleles↗
PubMed1995

Results of extensor tendon repair performed by junior accident and emergency staff.

The results of 46 extensor tendon repairs performed by junior accident and emergency doctors were assessed, with a minimum follow up of 6 months. Based on Miller's assessment, 80 per cent of the proximal injuries achieved excellent or good results. Only 18 per cent of distal injuries achieved excellent or good results. Neither grip or fingertip pinch strength were significantly reduced. Sixty-seven per cent of patients complained of no residual pain and only 7 per cent complained of the injured digit getting in the way.

Adolescent↗
PubMed1995

Techniques for the application of the analytical solution to the multicylinder somatic shunt cable model for passive neurones.

The general solution for the voltage response to a generic impulse current input in a multicylinder somatic shunt cable model for passive neurones has been developed in [1]. In this paper we consider the application of the multicylinder solution to examples previously considered by other authors for the single cylinder case: long and short current input and synaptic input modeled by an alpha-function and a multi-exponential function. Simple expansions appropriate for small and large times are found and efficient means of obtaining these expansions are clearly demonstrated. The dependence of the small and large time solutions upon the dimensionless parameters appearing in the conservation of current condition at the soma is investigated. Relevant limits of these dimensionless parameters which further simplify the small and large time solutions are related back to equivalent dimensional problems of interest to the practitioner. The well-posedness of the dimensionless inverse problem is investigated and a method proposed for the solution of the dimensional inverse problem for the somatic shunt.

Animals↗