PubMed Health⌕ Search

Biomedical subjects

L Johnson

Publications and source records attributed to L Johnson.

584 records · Page 33Linked to original sources
PubMedDate not supplied

Nurses in OR are more assertive than radiographers.

This study investigated two hypotheses: that there is a positive correlation between assertiveness and self-esteem, and that nurses rate lower than non-nurses on the constructs. A self-report survey incorporating scales for general assertiveness, situationally-specific assertiveness, global self-esteem and differentiated self-esteem was utilised. For the sample of 83 operating room nurses and 81 radiographers, correlations significant at the p < .001 level between the respective scales supported the first hypothesis. Analysis of variance yielded no significant differences between the two groups on either self-esteem measures or general assertiveness, with the nurses scoring significantly higher than radiographers on the situationally-specific assertiveness scale. Findings challenge the stereotype of the 'shrinking violet' nurse. Additional analysis revealed that the power component of differentiated self-esteem had a higher correlation with global self-esteem and with both assertiveness measures than any other component. Further, the operating room nurses were significantly more power-oriented than radiographers. The pre-eminence of power in the findings suggests that assertiveness and self-esteem are issues relating to the empowerment of nurses.

Allied Health Personnel↗
PubMedDate not supplied

Hereditary epidermolysis bullosa: oral manifestations and dental management.

Epidermolysis bullosa (EB) is a diverse group of disorders that have as a common feature blister formation with tissue separation occurring at variable depths in the skin and/or mucosa depending on the specific EB type. There may be marked oral involvement, potentially creating devastating alterations in the soft and hard tissues. Oral tissue fragility and blistering is common to all EB types. However, oral debilitation as a result of soft tissue scarring is primarily limited to the recessive dystrophic EB subtypes. Generalized enamel hypoplasia appears to be limited to junctional EB, although rampant dental caries is associated with many individuals having generalized recessive dystrophic EB. While systemic treatment remains primarily palliative, it is possible to prevent destruction and subsequent loss of the dentition through appropriate interventions and dental therapy. The majority of individuals with mild EB subtypes may receive dental treatment with only minor modifications in approach. Even the most severely affected individuals with EB can retain their dentition using general anesthesia and conventional restorative techniques. With aggressive preventive interventions and management of developing malocclusions using serial extraction, it also is possible to reduce the likelihood of rampant caries, achieve an acceptable occlusion without the need for active tooth movement or appliance therapy, and allow these individuals to benefit from maintaining a natural healthy dentition.

Anesthesia, Dental↗
PubMedDate not supplied

Testicular composition, number of A spermatogonia, germ cell ratios, and number of spermatids in three different breeds of boars.

Seminal quality, including the number of spermatozoa in the ejaculate, varies among breeds of boars. Variation in seminal quality may be explained by breed differences in testicular size and composition. The objective of this study was to characterize testicular composition and population sizes of germ cells and somatic cells in three different breeds of boars. Testes from mature and normal Meishan (M, n = 5; age 225 days), Whitecross (WC, n = 5; age 346 days), and West African (WA, n = 5; age 322 days) boars were either fixed in Zenker-formol or perfused with glutaraldehyde, embedded in Epon, sectioned at 0.5 microns or 20 microns and evaluated stereologically for germ cells, Leydig cells, Sertoli cells, and other testicular structures. The paired parenchymal weight was higher (P < 0.05) in the WC (498 +/- 35 g) than in the M (247 +/- 17 g) or WA (133 +/- 10 g). The nuclear volumes per boar of Sertoli cells, type A spermatogonia, leptotene, zygotene, pachytene, secondary spermatocytes, spermatids with spherical nuclei, and spermatids with elongated nuclei were higher (P < 0.05) in the WC than in the M or WA. The nuclear volumes per boar of blood vessels and Leydig cells were exceptionally higher (P < 0.05) in the M than in the WC or WA. The average germ cell nuclear diameters were similar (P > 0.05) for the M and WC but least (P < 0.05) in the WA breed. Also, the nuclear diameters of Leydig cells and Sertoli cells were higher (P < 0.05) in the M than in the WC or WA. The population sizes of all the intratubular components were positively correlated (P < 0.05) with testicular size (weight). Volume density of seminiferous tubules was similar in the WA and WC, but was lowest in the M, who had the highest density of Leydig cells. However, due to the larger testes, all germ cell types and Sertoli cells were higher in the WC than in the WA or M. The M and WA had similar low numbers of type A spermatogonia, but there was less term cell degeneration in M than in Wa, such that M spermatids were intermediate in number between WA and WC.

Animals↗
PubMedDate not supplied

Complications of anterior spinal surgery in children.

The purpose of this study was to document the medical and surgical complications of anterior spine surgery in children and to identify risk factors for complications. A retrospective chart review was conducted of 599 anterior procedures (24 anterior only, 300 staged anterior/posterior, 175 combined anterior/posterior procedures) performed between 1967 and 1991. Major complications occurred in 7.5% of procedures and minor complications in 33%. Risk factors for major complications were age > 14 years, male gender, kyphotic curve type, curve sizes > 100 degrees, vital capacity < 40% of predicted, and use of thoracotomy. Risk factors for minor complications were age > 14 years, curves > 100 degrees, vital capacity < 40% of predicted, and use of a staged procedure. Multivariate analyses of risk factors identified age > 14 years and curves > 100 degrees as the most significant risk factors for major complications and age > 14 years for minor complications. We concluded that anterior spinal surgery can be performed in children with an acceptable level of risk and that referral for surgery before 14 years of age and before the curve size progresses will significantly reduce the risk of complications.

Adolescent↗
PubMedDate not supplied

Heterotopic transplantation as a model to study the regulation of spermatogenesis; some histomorphological considerations about sperm decline in man.

A novel animal model (syngeneic neonatal testicular graft transplanted under the skin of the outer ear in adult inbred Fischer rats that had been castrated, hypophysectomised, and/or subjected to hormonal replacement therapy) was developed to study regulation of spermatogenesis and Sertoli cell number. Given that Sertoli cell number and testicular size are important in determining spermatozoan production rates, this model was first used to study Sertoli cell proliferation, testicular size, and establishment of germ cells. The specific objectives were to determine the developmental pattern of Sertoli cell numbers in transplanted testes and the effect of number of testes transplanted, sex of hosts, pituitary hormonal removal, and replacement on Sertoli cell number, hormonal status of the host, and establishment of germ cells. A few tubules had complete spermatogenesis at 90 days posttransplantation, indicating that Sertoli cells in some of these tubules were functional. Leydig cell structure appeared to be normal, but the density of these interstitial cells was greater than that in testes of intact rats. Although the weight of the seminal vesicles and prostate were maintained in the castrated host with transplants, both serum FSH and LH concentrations were higher than intact control rats. Leukocytic infiltration of testes was not observed in intact rats or in rats receiving neonatal testes. Although transplanted testes showed a delay in reaching the plateau value for Sertoli cell number per testis and although the value reached was lower than in intact testes, the developmental pattern of Sertoli cell proliferation (early division of cells followed by stabilized number of cells) in transplanted testes was similar to that in intact rats. Hypophysectomy reduced the growth of testicular grafts, and hormonal replacement via retransplantation to pituitary intact hosts enhances Sertoli cell proliferation and testicular growth. When two on four testes were transplanted into castrated males or ovariectomized female hosts for 65 days, there was no difference in the graft weights or Sertoli cell numbers between sexes of hosts. Four transplanted testes per rat produced more total testicular parenchyma and a greater number of Sertoli cells per testis than did two testes regardless of sex of the host. Transplantation of six or eight testes produced more total Sertoli cells/host than that found in testes of intact rats. Using hormonal therapy in hypophysectomized hosts, the testicular parenchymal weight was greater for pituitary-intact hosts and FSH-LH combination than the control media. There was no statistically significant difference among the media control, LH, FSH, and GH. This testicular transplant model has shown that the period of Sertoli cell proliferation can be delayed by hypophysectomy, that Sertoli cell number can be influenced by endogenous and exogenous hormones, and that a major component in regulation of testicular size is at the level of the testis. Hence, this model should facilitate study of experimental endocrine manipulation control and potential experimental intervention to increase Sertoli cell number, testicular size, and spermatogenesis. Regarding human sperm count decline in recent years, there appears to be no significant decline in Sertoli cell number or spermatogenic potential in a group of North American men. However, there was a significant decline in volume/man of Leydig cells and volume/man of Leydig cell cytoplasm.

Adult↗
PubMedDate not supplied

Cytoplasmic extrusion and the switch from creatine kinase B to M isoform are completed by the commencement of epididymal transport in human and stallion spermatozoa.

Although in several species there is a relationship between epididymal sperm transport and fertility, in human in vitro fertilization (IVF), spermatozoa recovered from the caput epididymidis or even the rete testis are fertile. We studied two objective markers of sperm maturity in the sperm of men and stallions: creatine kinase (CK) concentrations, which are a measure of cytoplasmic retention in immature spermatozoa, and the ratio of CK-M and CK-B isoforms (% CK-M/[CK-M + CK-B]), which is proportional to the incidence of mature sperm. The CK markers and the fertilizing function are closely related: Immature sperm with cytoplasmic retention do not bind to the zona, because during cytoplasmic extrusion, the sperm plasma membrane is also remodeled. We examined whether changes in sperm CK values are still ongoing during epididymal transport, or if cellular maturation is completed prior to the arrival of sperm in the caput epididymidis. The incidences of mature sperm in human caput and corpus epididymidis (studied in six men with obstructive azoospermia of various pathogeneses) were (mean+/-SEM) 55.7+/-2.2 and 49.3+/-7.6%, respectively; and the sperm CK-M ratios in the caput epididymidis of three men were 72, 75, and 70%, values that are similar to those of ejaculated sperm. In four segments of the proximal and distal epididymis of three stallions (the origin of sperm was also verified by the position of the cytoplasmic droplet) and in ejaculate of five stallions, the incidences of mature sperm were 88.2+/-6.2, 89.0+/-6.7, 90.3+/-7.8, 87.6+/-5.9, and 86.7+/-0.8%, and the respective CK-M ratios were 75.0+/-8.7, 84.2+/-2.9, 87.9+/-1.2, 92.5+/-1.5, and 69.3+/-3.5%. There were no differences in the incidences of mature and immature spermatozoa or in CK-M ratios among sperm arising from the various epididymal regions or from the ejaculate in men or stallions. Thus, the cellular maturation events in sperm, as detected by the CK markers, are completed by the time the sperm commences epididymal transport. These findings are in agreement with the IVF fertility of sperm aspirated from the male reproductive tract. The data may also suggest that the primary role of sperm epididymal transport in men is to remodel the plasma membrane to enhance sperm functional integrity in the diverse environments of the male and female reproductive tracts prior to fertilization.

Animals↗
PubMedDate not supplied

Ethnic differences in testicular structure and spermatogenic potential may predispose testes of Asian men to a heightened sensitivity to steroidal contraceptives.

Spermatogenesis in Asian men appears to be more susceptible to suppression by steroidal contraceptives administered in clinical trials than spermatogenesis in Caucasian men. The objective of this study was to determine whether ethnic differences exist in testicular structure and spermatogenic potential that might predispose Asians to a high sensitivity to steroidal contraceptives. Testes from 12 Chinese men were compared to those from 8 Hispanic men and 12 non-Hispanic Caucasian men of ages 29+/-3, 30+/-2, and 29+/-3 years, respectively. Testes were fixed by vascular perfusion with glutaraldehyde, further fixed in osmium, embedded in Epon, and evaluated by stereology using 0.5-microm sections stained with toluidine blue. Homogenates of fixed testes were evaluated for the number of Sertoli cells and the daily sperm production based on pachytene primary spermatocytes (PDSP) or spermatids with spherical nuclei (DSP). Paired parenchymal weight was less (P < 0.05) in Chinese men than in Hispanic or Caucasian men. The PDSP per gram of parenchyma was lower (P < 0.05) and the DSP per gram tended to be lower in Chinese men than in other groups. The histologic appearance, volume density, and length per man of seminiferous tubules were the same among the ethnic groups; however, the diameter of seminiferous tubules was less (P < 0.05) in Chinese than in Hispanic or Caucasian men. The PDSP per man and the DSP per man were lower (P < 0.05) in Chinese than in Hispanic or Caucasian men. The number of Sertoli cells per gram was higher (P < 0.05) in Chinese or Caucasian men than in Hispanic men, but the number of Sertoli cells per man was lower (P < 0.05) in Chinese men than in Hispanic or Caucasian men. Sertoli cell function, measured as the number of germ cells accommodated by a single Sertoli cell, was lower (P < 0.05) in Chinese men than in Caucasian men. The volume density of Leydig cell cytoplasm was greatest (P < 0.05) in Chinese men, but the number of Leydig cells was similar among the ethnic groups. Hence, smaller testes coupled with reduced Sertoli cell number and function and reduced daily sperm production could predispose Asian men to have a heightened negative response of testes to steroidal contraceptives, as compared to Caucasian men. Dampening (by exogenous androgens) of any physiological benefit to spermatogenesis that a high volume density of Leydig cell cytoplasm may bestow on the human testis (that Asian men may have evolved to require) would exacerbate ethnic differences in the spermatogenic response to hormonal contraceptives.

Adult↗