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Biomedical subjects

D Johnson

Publications and source records attributed to D Johnson.

At least 199 records · Page 11Linked to original sources
PubMed1998

A new pitheciin primate from the middle Miocene of Argentina.

We report here a new fossil primate from the middle Miocene of Argentina. The material consists of isolated teeth, mandibular fragments, and a talus. The fossils were collected in the Collón Cura formation at Cañadón del Tordillo in Neuquén Province. An age of 15.71 +/- 0.07 Ma has been reported for the Pilcaniyeu Ignimbrite, which lies just below the paleosols in which the fossils were found. This material is thus the youngest occurrence of fossil primates in Argentina (hitherto documented in the Santacrucian and older land mammal ages) but still is older than the middle Miocene platyrrhine primates from La Venta, Colombia, in particular the pitheciins Nuciruptor and Cebupithecia. The material is recognized as a new genus and species of Pitheciinae, Propithecia neuquenensis. The mesiodistally compressed, high-crowned incisors are specialized and similar to species in the tribe Pithecini and to the nonpitheciin Soriacebus (early Miocene, Patagonia). We rule out a phylogenetic relationship to the latter because of differences in molar morphology. Propithecia does, however, fit well into the pattern of pitheciin evolution, being more derived than the middle Miocene pitheciin Nuciruptor but not as much as another middle Miocene taxon, Cebupithecia. As such, this makes Propithecia the oldest taxon that can be confidently placed within this modern New World monkey subfamily. By analogy with the molar structures and diets of extant platyrrhines, Propithecia has a molar structure consistent with a variety of low-fiber diets ranging from fruit and gum to seeds. Its incisors suggest seed-eating in much the same way as extant pitheciins, like Pithecia. The talus resembles that of Callicebus, suggesting arboreal quadrupedal locomotion.

Animals↗
PubMed1998

The nonspecific inflammatory response to injury.

PURPOSE: The role of the nonspecific inflammatory response in causing injury related to surgery has become better understood over the last decade. There are complex interactions between neutrophils, cytokines and nitric oxide metabolites that may cause organ injury following surgery. The purpose of this review is to summarize some of the processes causing injury through these nonspecific pathways. METHODS: A review of the medical and anaesthetic literature related to inflammation, neutrophils and pro-inflammatory cytokines were performed using Medline. Bibliographies of relevant articles were searched and additional articles were then selected and reviewed. RESULTS: Pro-inflammatory cytokines, such as tumour necrosis factor, are released in response to a variety of noxious stimuli (e.g. burns, sepsis, or CABG surgery). These cytokines cause activation of neutrophils with increased upregulation of adhesion complexes on neutrophils and vascular endothelium. Nitric oxide synthase activity is also increased with a resultant increased production of nitric oxide. The increased nitric oxide concentration in the presence of superoxide free radicals secreted by activated neutrophils forms peroxynitrite, a more reactive and toxic molecule. Once this process is initiated, diffuse organ injury can result. Although some information related to specific anaesthetics is available, firm recommendations related to clinical practice cannot be made. CONCLUSIONS: There is a complex interplay of inflammatory mediators that can cause injury. Although specific clinical applications for manipulating these pathways are not yet generally available, this area holds promise to develop new techniques to improve outcomes following surgery.

Cell Adhesion Molecules↗
PubMed1998

The selective use of a single-stage and a two-stage technique for hypospadias correction in 157 consecutive cases with the aim of normal appearance and function.

This paper establishes the aim of normal function and appearance in hypospadias surgery. In order to meet this aim we have used a combination of a single-stage and a two-stage repair, both incorporating foreskin reconstruction. The technique of single-stage repair is illustrated using operative photographs. Our experience with 157 repairs in a 3-year period is described. Thirty-five single-stage repairs were completed with no complications; 122 two-stage repairs were carried out, in which a 5% fistula rate was achieved in primary cases. Salvage reconstruction had a higher incidence of complications.

Aged↗
PubMed1998

Novel trabecular meshwork inducible glucocorticoid response mutation in an eight-generation juvenile-onset primary open-angle glaucoma pedigree.

OBJECTIVE: This study aimed to update a large kindred with juvenile-onset primary open-angle glaucoma (POAG) first described in 1940 and to identify the underlying genetic cause of the disease. DESIGN: Molecular genetic study of a single kindred, including clinical examination, retrospective review of clinical and family history records, linkage analysis, and mutation screening. PARTICIPANTS: The retrospective review included 957 members of a single large family. The linkage study included 40 members of 1 branch of the family in which juvenile-onset POAG is segregating in an autosomal-dominant pattern. Mutation screening included 15 at-risk family members with juvenile-onset POAG, probands of 40 families with adult-onset POAG, probands of 11 additional unrelated juvenile-onset POAG families, and 43 unrelated normal control subjects. INTERVENTION: Clinical and family history records were obtained, ophthalmologic examinations were performed, and blood samples were drawn for use in genotyping. MAIN OUTCOME MEASURES: Allele sizes of microsatellite repeat genetic markers from the vicinity of the GLC1A glaucoma gene on chromosome 1q were assigned based on size fractionation of DNA fragments generated by polymerase chain reaction (PCR). Linkage was established by the method of lod scores. Mutations were identified by determination of the DNA sequence of PCR products amplified from the trabecular meshwork inducible glucocorticoid response (TIGR) gene. Glaucoma status for purposes of linkage and mutation analysis was based on a combination of ophthalmologic examination, clinical records, family history, and previously published information. For some individuals reported in the pedigree, but not included in the genotyping studies, less information was available as presented in the text and tables. RESULTS: Autosomal-dominant POAG was confirmed or reported for 78 members of an 8-generation family. Linkage analysis showed significant evidence for linkage of juvenile-onset POAG in one branch of the family to D1S452 (maximum lod score of 6.42 at a recombination fraction of 0.00) and other markers in the vicinity of the GLC1A gene on chromosome 1q. Screening of the TIGR gene identified a mutation that results in substitution of asparagine for isoleucine at codon 477 near the carboxyterminal end of the protein. CONCLUSIONS: The authors' findings strongly suggest that the juvenile-onset POAG locus in this family is the GLC1A locus and that the underlying cause of the disease is the IIe477Asn TIGR mutation that cosegregates with juvenile-onset POAG in one branch of this large family. Lack of samples from deceased individuals prevented the authors from determining whether reported adult-onset cases in this family could also be attributed to the IIe477Asn TIGR mutation. Absence of the IIe477Asn TIGR mutation from other juvenile- and adult-onset POAG families implies that this TIGR mutation is not a common cause of glaucoma.

Adolescent↗
PubMed1998

Disseminated histoplasmosis in an infant with acquired immunodeficiency syndrome.

Disseminated histoplasmosis has been recognized as a serious opportunistic infection in patients with acquired immunodeficiency syndrome (AIDS). However, cases reported in the literature have been predominantly in adult patients. Here we report an infant with AIDS who presented with fever, cough, rhinorrhea, hepatosplenomegaly, pancytopenia and coagulopathy, and died of respiratory failure. Autopsy revealed disseminated histoplasmosis involving multiple organs including lungs, intestines, liver, spleen, bone marrow, lymph nodes, kidneys, and meninges. The diagnosis was established based on histomorphology and confirmed by blood culture.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Recommended components of health care provider training programs on intimate partner violence.

Programs that are effective in training health care providers to recognize and meet the needs of victims of intimate partner violence must be identified and replicated. The Centers for Disease Control and Prevention (CDC) has developed criteria for use in developing, enhancing, and evaluating such programs. CDC developed these criteria as a result of continuing efforts to provide useful products for constituents through literature reviews and consultations with experts in the field; evaluations of training programs; creation of an inventory and annotated bibliography of health care provider training programs in the United States and Canada; and development of a framework to assist hospitals and health centers in evaluating their training programs. Training should begin while providers are in professional school and continue in the health care setting. Curricula should be multidisciplinary and should provide information, promote clinical skills, and effectively link providers with resources. Evaluation should assist programs in determining providers' needs and identifying appropriate materials, trainers, and training strategies. CDC is working to establish scientific evidence that provider training programs are effective and to share successful models with others. Providers have an important role in stopping and ultimately preventing intimate partner violence, but they are not alone in this effort. They need to know how to access the growing network of assistance including women's advocates, the criminal justice system, and other members of increasingly dynamic community coalitions.

Canada↗
PubMed1998

Endothelial damage due to ischemia and reperfusion is prevented with SIN-1.

BACKGROUND: Acute ischemia followed by reperfusion results in direct endothelial damage characterized by cell swelling, increased permeability and loss of acetylcholine-mediated vasorelaxation. Ischemia followed by reperfusion in a New Zealand white rabbit hindlimb has been shown to result in loss of acetylcholine-induced relaxation of superficial femoral arteries. This loss of relaxation in response to acetylcholine is a reflection of the decreased nitric oxide availability that occurs with reperfusion injury. The purpose of this investigation was to evaluate the effect of SIN-1, a direct nitric oxide donor, on this endothelial injury. METHODS: New Zealand white rabbits underwent complete ischemia of the right hindlimb for 3 h followed by 2 h of reperfusion. Aliquots of 20 ml of either 0.88-mM SIN-1 or normal saline was infused via a lateral branch of the right common iliac artery during the first 20 min of reperfusion. Sham vessels were subjected to the 5-h operative intervention to control for anesthetic effect. Control vessels were harvested from rabbits not exposed to ischemia or reperfusion. Superficial femoral artery rings were evaluated in vitro for endothelial cell-mediated relaxation. Rings were contracted with potassium chloride and norepinephrine and then exposed to standardized incremental doses of acetylcholine to measure percent relaxation. Artery sections were sent for hematoxylin and eosin staining. RESULTS: No significant differences were seen in contraction caused by either potassium chloride or norepinephrine in all four experimental groups. Saline infused vessel rings relaxed a mean of 8.42 +/- 2.39% and 49.57 +/- 8.65% in response to acetylcholine doses of 3 x 10(-8) M and 1 x 10(-7) M, respectively. In contrast, SIN-1 infused vessels relaxed a mean of 57.82 +/- 2.65% and 100.23 +/- 1.53% to the same doses of acetylcholine. Control and sham arteries showed a similar relaxation response as compared with SIN-1 infused vessels. Differences in relaxation when comparing saline infused vessels with SIN-1 infused, sham and control arteries, were significantly different at each dose of acetylcholine from 3 x 10(-8) M to 1 x 10(-7) M (P < 0.05, ANOVA). Histologic examination of the vessels revealed no morphologic differences among the experimental groups. All vessels were structurally normal with an intact endothelium. CONCLUSION: In this model of rabbit hindlimb ischemia, preservation of endothelial cell-mediated vasorelaxation occurs with administration of intra-arterial SIN-1 during reperfusion. This preservation of endothelial function cannot be explained by histologic changes in the arterial wall or attributed to altered arterial contractility in response to potassium chloride or norepinephrine.

Animals↗
PubMed1998

Endothelial damage due to ischemia and reperfusion is prevented with SIN-1.

BACKGROUND: Acute ischemia followed by reperfusion results in direct endothelial damage characterized by cell swelling, increased permeability and loss of acetylcholine-mediated vasorelaxation. Ischemia followed by reperfusion in a New Zealand white rabbit hindlimb has been shown to result in loss of acetylcholine-induced relaxation of superficial femoral arteries. This loss of relaxation in response to acetylcholine is a reflection of the decreased nitric oxide availability that occurs with reperfusion injury. The purpose of this investigation was to evaluate the effect of SIN-1, a direct nitric oxide donor, on this endothelial injury. METHODS: New Zealand white rabbits underwent complete ischemia of the right hindlimb for 3 h followed by 2 h of reperfusion. Aliquots of 20 ml of either 0.88-mM SIN-1 or normal saline was infused via a lateral branch of the right common iliac artery during the first 20 min of reperfusion. Sham vessels were subjected to the 5-h operative intervention to control for anesthetic effect. Control vessels were harvested from rabbits not exposed to ischemia or reperfusion. Superficial femoral artery rings were evaluated in vitro for endothelial cell-mediated relaxation. Rings were contracted with potassium chloride and norepinephrine and then exposed to standardized incremental doses of acetylcholine to measure percent relaxation. Artery sections were sent for hematoxylin and eosin staining. RESULTS: No significant differences were seen in contraction caused by either potassium chloride or norepinephrine in all four experimental groups. Saline infused vessel rings relaxed a mean of 8.42 +/- 2.39% and 49.57 +/- 8.65% in response to acetylcholine doses of 3 x 10(-8) M and 1 x 10(-7) M, respectively. In contrast, SIN-1 infused vessels relaxed a mean of 57.82 +/- 2.65% and 100.23 +/- 1.53% to the same doses of acetylcholine. Control and sham arteries showed a similar relaxation response as compared with SIN-1 infused vessels. Differences in relaxation when comparing saline infused vessels with SIN-1 infused, sham and control arteries, were significantly different at each dose of acetylcholine from 3 x 10(-8) M to 1 x 10(-7) M (P < 0.05, ANOVA). Histologic examination of the vessels revealed no morphologic differences among the experimental groups. All vessels were structurally normal with an intact endothelium. CONCLUSION: In this model of rabbit hindlimb ischemia, preservation of endothelial cell-mediated vasorelaxation occurs with administration of intra-arterial SIN-1 during reperfusion. This preservation of endothelial function cannot be explained by histologic changes in the arterial wall or attributed to altered arterial contractility in response to potassium chloride or norepinephrine.

Animals↗
PubMed1998

A new method to examine very low birth weight fetal and hebdomadal mortality in a regionalized system of perinatal care.

OBJECTIVE: Aggressive maternal transport of very low birth weight (VLBW) live births from community hospitals to regional perinatal centers may artificially increase community fetal death rates. By allocating maternal transports according to the location of antepartum and intrapartum care and separately computing antepartum and intrapartum fetal mortality rates, a more appropriate measure of hospital-based mortality may be determined. METHOD: Delivery charts were reviewed for 568 VLBW deliveries (including 97 fetal deaths and 77 hebdomadal deaths) occurring between 1990 and 1992 in a geographically defined perinatal region. Maternal transports were analyzed with community hospitals for antepartum mortality rates and with the regional center for intrapartum mortality rates. RESULTS: Using traditional methods, the fetal mortality rates for community hospitals and the regional center were antepartum 385.1 vs. 45.2, respectively, and intrapartum 120.9 vs. 24.9, respectively. When regional center live births (maternal transports) are placed with community hospitals for analysis of antepartum mortality, the new antepartum mortality rates were 185.7 vs. 72.8, respectively. The hebdomadal mortality rate for community hospitals was 250.0 as compared to 145.8 for the regional center. CONCLUSION: Maternal transports to a regional center represent successful antepartum management by community care providers. Even though they delivered in the regional center, they should be analyzed with community hospitals for antepartum fetal mortality comparisons. Therefore, antepartum and intrapartum fetal mortality should be examined separately in a functioning regionalized perinatal care program where the location of patient care differs from location of delivery.

Adolescent↗
PubMed1998

Pleasure and pain in doing well, together: an investigation of performance-related affect in close relationships.

In a series of four studies, the self-evaluation maintenance (SEM) model is used to predict peoples' self-reported affective responses to doing better or worse than their partners. Both self-protective reactions to comparison (i.e., those predicted by the original SEM model) and empathic reactions to the partner's response (i.e., those predicted by the extended SEM model) were obtained. In addition, as predicted on the basis of both models, comparisons with romantic partners resulted in a different pattern of self-reported affect than did comparisons with strangers. Unexpectedly, it appeared that empathic effects were minimal or absent among dating partners when comparisons were in areas of high self-relevance.

Achievement↗
PubMed1998

A theoretical investigation of reference frames for the planning of speech movements.

Does the speech motor control system use invariant vocal tract shape targets when producing vowels and semivowels? A 4-part theoretical treatment favoring models whose only invariant targets are regions in auditory perceptual space over models that posit invariant constriction targets is presented. Auditory target regions are hypothesized to arise during development as an emergent property of neural map formation in the auditory system. Furthermore, speech movements are planned as trajectories in auditory perceptual space. These trajectories are then mapped into articulator movements through a neural mapping that allows motor equivalent variability in constriction locations and degrees when needed. These hypotheses are illustrated using computer simulations of the DIVA model of speech acquisition and production. Finally, several difficult challenges to proponents of constriction theories based on this theoretical treatment are posed.

Humans↗
PubMed1998

Speciation of arsenic metabolites in the urine of occupational workers and experimental rats using an optimised hydride cold-trapping method.

A hydride cold-trapping technique was developed and optimised for the measurement of urinary arsenic metabolites. The analytical precision of the method was found to be 6.1, 4.0 and 4.8% (n = 5) for inorganic arsenic (ASi), monomethylarsonate (MMA) and dimethylarsinate (DMA), respectively, with recoveries close to 100%. The detection limits were 1.0, 1.3 and 3 ng for ASi, MMA and DMA, respectively. The method was then used to analyse urine samples obtained from three groups of workers for occupational exposure in three companies where copper chrome arsenate was used for timber treatment. The results were compared with those for a normal control group of laboratory workers. Arsenic and its metabolites were also measured in experimental rats given 5 mg As kg-1 body mass by oral gavage in the form of sodium arsenite, calcium arsenite or sodium arsenate. Occupational workers showed a significantly higher excretion of ASi. Up to two fold increases of urinary ASi excretion in rats compared with control rats were also observed in animals dosed with various forms of arsenicals. The method is suitable for the measurement of arsenic metabolites in urine of both humans and experimental animals.

Animals↗
PubMed1998

Communicative competence as perceived by adults with severe speech impairments associated with cerebral palsy.

The effects of aided message length (single-word vs. phrase-generated messages) and partner feedback (presence vs. absence of expanded message repetitions) on perceptions of the communicative competence of an adult augmentative and alternative communication (AAC) system user were examined. Subjects consisted of 12 nonambulatory adults with severe speech impairments associated with cerebral palsy. Four scripted videotaped conversational conditions involving the AAC system user and a typically speaking partner were employed to manipulate the two independent variables. A balanced incomplete block design was used. Following each viewing, subjects completed a questionnaire designed to assess the communicative competence of the AAC system user. Results indicated that neither independent variable had an impact on the subjects' ratings of communicative competence. Findings are compared with those from an earlier investigation, and clinical implications are discussed.

Adult↗
PubMed1998

Monocyte tissue factor-like activity in post myocardial infarction patients.

It is widely recognized that thrombosis is the major event in the evolution of stable vascular disease to unstable ischaemic syndromes including myocardial infarction and stroke. The purpose of this case-control study was to establish clinical and laboratory data on the possible relationship between specific components of the haemostatic system and coronary heart disease. The procoagulant activity (PCA) of peripheral monocytes and polymorphonuclear neutrophils was assessed in 21 males who had suffered a myocardial infarction (MI) and in age-matched controls. In addition, total factor VII activity, fibrinogen, tissue factor pathway inhibitor (TFPI). D-dimers, tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI-1), tumour necrosis factor-alpha (TNF-alpha) and full blood counts were measured. Post MI patients had significantly higher monocyte PCA, higher plasma concentrations of TFPI, fibrinogen, t-PA, T/P100 and also higher total white blood cell and neutrophil counts compared to age-matched controls. This elevated procoagulant state in post MI patients could further exacerbate the disease process and increase the risk of subsequent acute ischaemic events.

Blood Cell Count↗
PubMed1998

Overt albuminuria predicts diabetic retinopathy in Hispanics with NIDDM.

Non-insulin-dependent diabetes mellitus (NIDDM) occurs with a higher frequency in Hispanic as compared with non-Hispanic whites. It also appears that there is a higher prevalence of diabetic nephropathy in the Hispanic population when compared with non-Hispanic whites. In the current study, 144 Hispanics and 671 non-Hispanic white NIDDM subjects were studied to determine the possible association of various risk factors and diabetic complications, including overt albuminuria, with diabetic retinopathy. Stereoscopic retinal fundus photographs were obtained and graded by the University of Wisconsin Fundus Photographic Reading Center. We also sought to determine whether risk factors for retinopathy vary between Hispanics and non-Hispanic whites. In the total group, duration of diabetes, glycosylated hemoglobin, neuropathy, diastolic hypertension, use of insulin, and Hispanic ethnicity correlated with the presence of retinopathy. Controlling for severity and duration of diabetes, Hispanics had a significantly increased risk of retinopathy relative to non-Hispanic whites (OR = 2.13, 95% CI = 1.34, 3.37, P = 0.0013). Duration of diabetes and presence of neuropathy were significantly correlated with the presence of diabetic retinopathy in Hispanics and non-Hispanic whites. The presence of overt albuminuria (>200 microg/min), although not related to diabetic retinopathy in non-Hispanic whites, conferred a high risk for diabetic retinopathy in Hispanics (OR = 11.14, CI = 1.20, 103.39, P = 0.0339) independent of other risk factors. In summary, Hispanics with NIDDM have an increased prevalence of diabetic retinopathy when compared with non-Hispanic whites. In addition, overt albuminuria in the Hispanic subjects appears to be a powerful predictor of the diabetic retinopathy.

Albuminuria↗
PubMed1998

Influence of the postoperative period and surgical procedure on ambulatory blood pressure-determination of hypertension load after successful surgical repair of coarctation of the aorta.

AIMS: This study quantified hypertension load using 24-h ambulatory blood pressure monitoring after successful repair of coarctation of the aorta less than (1) or more than 10 years previously (2) and examined the influence of the surgical procedure (anastomosis or subclavian flap). METHODS AND RESULTS: Ambulatory blood pressure recordings were obtained using an Accutracker II monitor every 30 min during the day and hourly, at night. Day and night systolic and diastolic values were higher in coarctation of the aorta than in controls: (day: systolic blood pressure/diastolic blood pressure: 133/71 +/- 6/4 vs 115/66 +/- 3/2 night: systolic blood pressure/diastolic blood pressure: 117/61 +/- 4/4 vs 107/57 +/- 3/2 mmHg, P < 0.01) and at all times, were higher in coarctation of the aorta (2) than in coarctation of the aorta (1). Clinical daytime systolic hypertension was observed in 20% of recordings from coarctation of the aorta (1) and 49% from coarctation of the aorta (2) while diastolic hypertension was not observed. However, systolic blood pressure and diastolic blood pressure responses to daily activities were significantly higher in coarctation of the aorta than in controls and this was more marked in coarctation of the aorta (2) than in coarctation of the aorta (1). Type of surgery did not affect either hypertension prevalence or blood pressure reactivity. CONCLUSIONS: These observations indicate exaggerated systolic blood pressure and diastolic blood pressure reactivity after repair of coarctation of the aorta, the prevalence of systolic hypertension doubling 10 years after surgery.

Adolescent↗
PubMed1998

A comprehensive screen for TWIST mutations in patients with craniosynostosis identifies a new microdeletion syndrome of chromosome band 7p21.1.

Mutations in the coding region of the TWIST gene (encoding a basic helix-loop-helix transcription factor) have been identified in some cases of Saethre-Chotzen syndrome. Haploinsufficiency appears to be the pathogenic mechanism involved. To investigate the possibility that complete deletions of the TWIST gene also contribute to this disorder, we have developed a comprehensive strategy to screen for coding-region mutations and for complete gene deletions. Heterozygous TWIST mutations were identified in 8 of 10 patients with Saethre-Chotzen syndrome and in 2 of 43 craniosynostosis patients with no clear diagnosis. In addition to six coding-region mutations, our strategy revealed four complete TWIST deletions, only one of which associated with a translocation was suspected on the basis of conventional cytogenetic analysis. This case and two interstitial deletions were detectable by analysis of polymorphic microsatellite loci, including a novel (CA)n locus 7.9 kb away from TWIST, combined with FISH; these deletions ranged in size from 3.5 Mb to >11.6 Mb. The remaining, much smaller deletion was detected by Southern blot analysis and removed 2,924 bp, with a 2-bp orphan sequence at the breakpoint. Significant learning difficulties were present in the three patients with megabase-sized deletions, which suggests that haploinsufficiency of genes neighboring TWIST contributes to developmental delay. Our results identify a new microdeletion disorder that maps to chromosome band 7p21.1 and that causes a significant proportion of Saethre-Chotzen syndrome.

Acrocephalosyndactylia↗