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Biomedical subjects

L Johnson

Publications and source records attributed to L Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1997

Fat embolism with the use of intraosseous infusion during cardiopulmonary resuscitation.

The objective of this prospective study was to assess the incidence and magnitude of fat emboli after cardiopulmonary resuscitation and intraosseous infusions. An animal laboratory at a university center was used to study 33 mixed-breed piglets. The piglets underwent hypoxic cardiac arrest followed by chest compressions and mechanical ventilation for a minimum of 30 minutes. The animals were divided in groups: group 1 (n = 5), which had no intraosseous cannulas, group 2 (n = 6), which had intraosseous cannulas with infusion, groups 3 (n = 6), 4 (n = 6), and 5 (n = 8), which had intraosseous cannulas with infusion of epinephrine, normal saline, and sodium bicarbonate respectively, and group 6 (n = 2), which was a sham group with no intraosseous cannulas and no cardiopulmonary resuscitation. At cessation of cardiopulmonary resuscitation, representative lung samples were collected from upper and lower lobes of each lung and observed for fat globules and bone marrow elements. Fat globules were seen in the peribronchial blood vessels and intravascular areas throughout all lung fields of groups 1 through 5. There was no difference in appearance or distribution of fat globules among the 5 treatment groups. Analysis of variance showed no statistical significance (P < 0.05) within or among groups 1 through 5. The use of the intraosseous cannula for infusion of emergency drugs and fluids did not increase the magnitude of fat embolization over cardiopulmonary resuscitation alone in this animal model. The benefits of using this procedure in critically ill children as a means of rapid vascular access for resuscitation is well established. However, the risk of fat embolism in this population needs further study.

Analysis of Variance↗
PubMed1997

The relationship between the concentration of ionised calcium and parathyroid hormone-related protein (PTHrP[1-34]) in the milk of mares.

Once lactation is established in mares, there is little change in the ionised calcium concentration in their milk. In contrast, the concentration of PTHrP(1-34) in the milk increases to a maximum level by the end of the second week of lactation, near which it remains for the rest of the lactation. As found in other species, the concentration of PTHrP(1-34) in mare's milk is considerably higher than that in plasma, sampled at the same time. No significant correlation could be demonstrated between the concentrations of PTHrP(1-34) and ionised calcium in the milk except during the last 10 weeks of lactation.

Animals↗
PubMed1997

Commitment to the underserved: evaluating the effect of an extracurricular medical student program on career choice.

BACKGROUND: This study was conducted to compare the practice locations and characteristics of physicians who participated as medical students in an extracurricular program to foster interest in careers of service to medically underserved populations with those of their classmates who did not participate in the program. METHODS: Using a mailed questionnaire, we conducted a cross-sectional study of graduates from the classes of 1983-1987 at one southwestern, public medical school. All Commitment to Underserved People (CUP) participants (n = 94) and a random sample of nonparticipating classmates (n = 188) were surveyed. CUP is an extracurricular project with components in each of 4 years of medical school that provides peer and faculty support, curriculum enrichment, and direct service to medically underserved populations. Outcome measures included the size of community of practice, practice type, and practice patient characteristics. RESULTS: Sixty seven (71%) of CUP participants and 126 (67%) of nonparticipants responded. CUP participants were more likely to be women, to specialize in family practice, to practice in the Indian Health Service (IHS) or overseas, to be located in a community of 25,000 or less, and to have participated in the state, service-payback loan program. In multiple regression, the specialty of family practice was associated with practice in a small community, the IHS, and a community health center; CUP participation was correlated with practice in small communities, the IHS, and a foreign country. CONCLUSIONS: Participation in the CUP program was associated with the specialty choice of family practice and with practice in settings associated with medically underserved populations. The CUP program has been successful in sustaining entering medical students' interests in underserved practice.

Journal Article↗
PubMed1997

A functional determinant in human luteinizing hormone and chorionic gonadotropin: differential effect of mutations about beta-GLN-54.

There is evidence that the conserved glutamine at residue 54 in the beta-subunit of human LH and and CG (hCG) is important for biological activity. Mutation to Arg in LH has been reported to impair receptor binding, leading to a documented case of hypogonadism, whereas in hCG the mutation has been shown to result in defective subunit association. Functional distinctions between LH and hCG have been described, but the significance of peptide-chain differences between the two has not been investigated systematically. We therefore compared the role of Gln-54 and its neighboring residues in both hormones, through replacement by amino acids with contrasting properties using site-directed mutagenesis. The mutant subunits were coexpressed with alpha-subunit in mammalian (Chinese hamster ovary) cells and the secreted hormones assayed for heterodimer formation, receptor binding, and steroidogenesis in murine Leydig cell tumor (MA-10) cells. Basic (Arg, Lys) substitution for Gln-54 in either hormone markedly impaired subunit association (<20% of wild-type) and the heterodimers that were formed were inactive (<5% of wild-type) in both assays. Arg-substituted hCG was also inactive in an adenylate cyclase assay using HEK-293 cells expressing rat LH/hCG receptor. After acidic (Glu) or neutral (Ala) substitution, heterodimer formation was less impaired (50-60% of wild-type), but effects on receptor interaction differed between the two hormones. The LH mutants still lacked binding activity, whereas the hCG products were fully active. The importance of residue 54 for receptor interaction appears to be sharply localized because mutation at adjacent positions (Pro-53 and Val-55) did not impair the activity of either hormone. Diminished heterodimer formation by Ile-53 mutation in LH (but not hCG), together with the similar effects of basic mutations at 54, imply long-distance effects as these residues are remote from alpha in the crystal structure. Our findings indicate that position 54 in LH and hCG is a determinant for both subunit association and receptor interaction. The differing responses between LH and hCG to certain mutations suggest that structural characteristics of the peptide chains may confer functional differences despite their close sequence homology.

Adenylyl Cyclases↗
PubMed1997

Maltreatment of children born to women who used cocaine during pregnancy: a population-based study.

BACKGROUND: Previous studies of maltreatment of children born to women who used cocaine during pregnancy have relied on either selected samples of infants identified at birth or biased, high-risk samples referred to protective services. OBJECTIVE: To determine the relative risk of either maltreatment or placement outside the home during the first 2 years of life in children born to women who used cocaine during pregnancy compared with a sociodemographically similar comparison group. PATIENTS: We reviewed the medical records of consecutive deliveries at Yale-New Haven Hospital from August 1, 1989 through September 30, 1990. Of the 1140 women who were eligible for the study, 173 had a positive history and/or a positive urine test for cocaine; 139 of the infants were included in the study. A comparison group of infants was chosen from 526 women whose obstetric records indicated that they had not used cocaine during pregnancy based on at least two separate notations in the record. For each of the 139 cocaine-exposed infants, an infant was chosen from the comparison group based on seven matching characteristics: date of birth, race, method of payment for the hospitalization, gestational age, mother's parity, mother's age at delivery, and timing of the first prenatal visit. MAIN OUTCOME MEASURES: Children's medical records at the only two hospitals in the region, the two neighborhood health centers, and the only health maintenance organization were reviewed from birth to 2 years of age. Each injury was classified by two independent reviewers who used predefined criteria to distinguish maltreatment (physical abuse, neglect, or abandonment) from unintentional injuries. Placements outside the home were categorized according to whether the placement was in foster care or with a relative. MAIN RESULTS: The children were mainly African-Americans (80%), and most were enrolled in Medicaid (96.5%). By 2 years of age, 9.3% of the infants in the cocaine-exposed group versus 1.4% in the comparison group had been maltreated [matched relative risk = 6.5; 95% confidence interval (CI) = 1.47, 28.80], and 25.9% vs 8.6% had spent some time in placement (matched relative risk = 5.0; 95% CI = 2.08, 12.01). After controlling for differences between the groups in baseline clinical and social variables, the adjusted odds ratios for both maltreatment (3.98; 95% CI = .81, 22.80) and placement (1.66; 95% CI = .74, 17. 83) decreased and were no longer statistically significant. CONCLUSION: In this population-based study, children born to women who used cocaine during pregnancy were at a substantially increased risk of maltreatment or placement outside the home compared with a sociodemographically similar comparison group. Differences in baseline variables between the two groups, however, partially accounted for this increased risk. Therefore, a mother's use of cocaine is more likely a marker of increased risk rather than a single explanatory variable.

Adult↗
PubMed1997

Behavioral pattern of dairy cows milked in a two-stall automatic milking system with a holding area.

Behavioral pattern was investigated in dairy cows milked in an automatic milking system (AMS) in contrast to cows milked in a conventional milking parlor. Forty-eight Holstein cows were allocated to two groups of 24 animals. The two groups were housed in adjacent free stall pens. Both groups were milked twice a day at 0500 and at 1500 for 30 d before commencement of the experiment, one in a two-stall AMS (AMS Group), the other in a 16-stall herringbone parlor (Parlor Group). The respective holding areas were used to encourage cows to enter the milking compartments. All cows consumed total mixed rations ad libitum, provided once a day between 0500 and 0600 in indoor feed bunks. Cows in both groups were allowed daily access to two adjacent outdoor paddocks from 1030 to 1230. Behavioral observations were carried out in the free stall barn from 0400 to 0900 and from 1250 to 1900 for 30 d. The number of cows lying down, standing in the stalls, standing in the passageway, and eating was recorded every 10 min. Analyses of variance were used to compare time serial changes in behavioral states between groups. Although the time serial changes in the behavioral states were not different between groups after returning from paddocks, they became significantly different between groups for all four recorded behavioral states after the onset of milking. Ethograms during the 11-h observation period showed that cows in the AMS group spent less time eating at the feed bunk and standing in the stalls to compensate for the longer time standing in the holding area. The results indicate that AMS milking with a holding area affects social synchronization of cows eating and resting and reduces time spent eating significantly more than parlor milking.

Aging↗
PubMed1997

Impaired neuropsychological performance in euthymic patients with recurring mood disorders.

BACKGROUND: Both patients suffering from schizophrenia and patients suffering from recurring mood disorder show cognitive impairments as established by a variety of neuropsychological tests. The aim of the present study was to investigate the neuropsychological performance of euthymic patients who had recurring mood disorder and the possible relationship between episodes of hospitalization and cognitive impairments. METHOD: Twenty-six euthymic patients with a DSM-III-R recurring mood disorder diagnosis were investigated by using the Synonym Reasoning and Block-Test Battery and a part of the Halstead-Reitan Test Battery. RESULTS: An overall lowered performance in the test results was found. There was a significant positive relationship between four different tests and the number of hospitalization episodes; the patients with impaired cognitive functioning had significantly more hospitalization episodes than patients with normal cognitive functioning. CONCLUSION: The results suggest that a subgroup of patients with recurring mood disorder are defined by more relapses and episodes of hospitalization and show cognitive dysfunctions even when euthymic.

Adult↗
PubMed1997

Caring for children and adults on a specialty unit.

The nursing care system in a university hospital was modified to accommodate children on an organ transplant unit. System components for ensuring high-quality care for patients of all ages are identified and described. Primary nursing, a Pediatric Nursing Practice Council, Child Family Life and the support of the health care team are incorporated to successfully care for adults and children on this specialty unit.

Adult↗
PubMed1996

Isolated pancreas rejection in combined kidney pancreas tranplantation.

The clinical success of pancreas transplantation is limited by the difficulty in diagnosing rejection. In simultaneous pancreas kidney (SPK) transplantation, the diagnosis of pancreatic rejection is particularly difficult in the absence of clinical evidence of kidney rejection. Moreover, patients receiving only pancreas grafts will not have a concomitantly grafted kidney to serve as a "sentinel" for rejection. Percutaneous pancreas graft biopsy has been reported in a few small series but has not been adopted for broad clinical use. We describe the evaluation of 69 consecutive episodes of suspected isolated pancreas allograft rejection by percutaneous pancreas allograft biopsy. These rejection episodes occurred in 41 patients with bladder-drained pancreas transplants (25 SPK, 14 pancrease after kidney transplants [PAK], amd two pancreas transplant alone [PTA]). The indications for percutaneous pancreas biopsy were a twofold or greater increase in serum amylase or lipase, or a sustained 40% to 50% drop in urine amylase in the setting of no evidence of renal allograft dysfunction in SPK transplants. Biopsies were performed with color-flow Doppler ultrasound localization using an 18-gauge automated biopsy needle. Pancreatic tissue adequate for histologic evaluation was obtained in 61 of 69 cases (88%). There were two cases of intraabdominal bleeding, one of which required surgical intervention; the other resolved spontaneously. Histologic assessment of the biopsies demonstrated varying degrees of acute cellular rejection in 48 of 61 specimens (79%). Twelve specimens (20%) were free of histologic evidence of rejection, and one specimen (2%) showed acute pancreatitis. At the time of suspected rejection mean serum amylase and lipase values were increased 3.6 and 8.3-fold, respectively, and urine amylase was decreased by a mean of 45%. We conclude that the commonly used markers for pancreas allograft rejection are only about 80% specific for acute rejection. Percutaneous pancreas allograft biopsy is safe and allows the avoidance of unnecessary antirejection therapy with its attendant side effects and cost.

Adult↗
PubMed1996

Disparities in clinical laboratory performance for blood lead analysis.

OBJECTIVE: To evaluate the validity of blood lead analysis for clinical specimens. DESIGN: We submitted blood lead samples with a known lead concentration, in a blinded fashion, as clinical specimens to 18 laboratories. These laboratories were surveyed for the following characteristics that were hypothesized to be related to assay validity: laboratory ownership (state vs private), participation in the Centers for Disease Control Blood Lead Proficiency Program, assay method, and price. Each laboratory received 6 specimens with an actual blood lead (ABPb) concentration of 0.43 mumol/L (9 micrograms/dL) and 3 additional specimens--each with an ABPb concentration of 0.33, 0.89, and 1.59 mumol/L (6.9, 18.4, and 32.9 micrograms/dL, respectively). OUTCOME MEASURES: Misclassification error rates for reporting an elevation ( > or = 0.48 mumol/L [ > or = 10 micrograms/dL) in the blood lead concentration, the within-laboratory mean and coefficient of variation (CV) (for multiple specimens with an ABPb concentration of 0.43 mumol/L [9 micrograms/dL]), and the adjusted odds of a reported blood lead concentration differing from those of an ABPb concentration by more than 0.14 mumol/L (3 micrograms/dL). RESULTS: Blood lead results were obtained for 157 of 162 submissions. One laboratory reported all blood lead specimens as "below 0.48 mumol/L (10 micrograms/dL)." Two (11%) of 18 specimens with an ABPb concentration of 0.89 mumol/L (18.4 micrograms/dL) and 1 (6%) of 17 with an ABPb concentration of 1.59 mumol/L (32.9 micrograms/dL) were classified as below 0.48 mumol/L (10 micrograms/dL); 2 (11%) of 18 with an ABPb concentration of 0.33 mumol/L (6.9 micrograms/dL) and 44 (42%) of 104 with an ABPb concentration of 0.43 mumol/L (9 micrograms/dL) were classified as 0.48 mumol/L or greater ( > or = 10 micrograms/dL). For specimens with an ABPb concentration of 0.43 mumol/L (9 micrograms/dL), the within-laboratory mean ranged from 0.23 to 0.52 mumol/L (4.8-10.7 micrograms/dL); the CV ranged from 3% to 37%. Laboratories that used anodic stripping voltammetry were 6.3 (95% confidence interval, 1.4-28.6) times more likely to report a specimen that differed from the ABPb concentration by more than 0.14 mumol/L (3 micrograms/dL) than those that used atomic absorption methods. No other laboratory characteristic predicted discordance between the reported blood lead and ABPb concentrations. CONCLUSIONS: This study documents wide variation in the validity of the blood lead measurement among clinical laboratories. While the performance of some laboratories far exceeded the criteria of the Centers for Disease Control Blood Lead Proficiency Program, others made large errors that could have resulted in the false-negative misclassification of children with significant lead exposure. Given these differences, the purchasers of laboratory services may require access to laboratory proficiency data to make rational choices among clinical laboratories. Further study of laboratory performance on clinical specimens is required to determine if order-of-magnitude errors occur with sufficient frequency to warrant routine submission of blinded quality control specimens by proficiency programs and to determine the cause of the poor performance of laboratories that used the anodic stripping voltammetry methodology.

Clinical Laboratory Techniques↗
PubMed1996

Five year trends in cardiac catheterization: a report from the Registry of the Society for Cardiac Angiography and Interventions.

The Society for Cardiac Angiography and Interventions has maintained a registry of cardiac catheterizations since 1979 and of percutaneous cardiac interventions since 1990. Data from 392,923 procedures (317,592 diagnostic catheterizations, 74,963 coronary interventions, and 368 valvuloplasties) for the years 1990-1994 inclusive are presented. Over the 5 year period there was a trend toward same day and 23 hr discharges (19% in 1990 to 29% in 1994), and a decrease in combined right and left heart procedures from 38% to 26%. For cardiac catheterizations ionic contrast use declined from 26% of procedures to 13% in 1994. The use of ionic contrast was even lower in interventional procedures, with laboratories reporting use in 21% of procedures in 1990 dropping to 9% in 1994. Balloons were the first choice device in 92.5% of native arteries and 82.7% of grafts in 1994. For the first time in 1994 more mitral than aortic valvuloplasties were reported.

Angioplasty, Balloon, Coronary↗
PubMed1996

Effects of developmental exposure to indole-3-carbinol or 2,3,7,8-tetrachlorodibenzo-p-dioxin on reproductive potential of male rat offspring.

Treatment of pregnant female Sprague-Dawley rats on Gestational Day 15 with a single oral dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (0.5, 1.0, or 2.0 micrograms/kg) or indole-3-carbinol (I3C, 1.0 or 100 mg/kg), an aryl hydrocarbon (Ah) receptor agonist which is found in cruciferous vegetables, resulted in reproductive abnormalities in the male offspring (three to five litters in each treatment group). Anogenital distance and crown to rump length were altered by both compounds; however, the timing of the effects (Day 1 or 5) was variable and the responses were not necessarily dose-dependent. In 62-day-old offspring, seminal vesicle (24 to 26%), prostate (32 to 44%), testicular parenchymal (14%), and epididymal weight (19%) were decreased by one or more doses of TCDD. In contrast, I3C at one or more doses decreased daily sperm production/g testicular parenchyma (13 to 20%) and daily sperm production/testis (22%). Total number of sperum in the epididymis was significantly decreased (30 to 33%) in rats perinatally exposed to TCDD and this was due to a decreased (49 to 51%) number of sperm in the tail of the epididymis. Perinatal exposure to I3C did not affect any of these parameters. TCDD did not affect epididymal transit time of sperm through the complete epididymis at any of the doses (0.5 to 2.0 micrograms/kg). However, at the two highest doses (1.0 and 2.0 micrograms/kg), TCDD increased epididymal transit rate of sperm through the tail of the epididymis by 33 and 37%, respectively. In contrast, primarily due to decreased transit rate (39%) of sperm through the head plus body of the epididymis. I3C (1 mg/kg) significantly increased total epididymal transit time by 31%. In conclusion, perinatal exposure of pregnant rats to I3C, an Ah receptor agonist similar to TCDD, causes reproductive abnormalities in male rat offspring; however, I3C and TCDD elicited both common and different responses.

Animals↗
PubMed1996

Partial wave in human seminiferous tubules appears to be a random occurrence.

Serial cross sections were evaluated to determine the architectural arrangement of stages among men with varied spermatogenic efficiencies. Using autopsy specimens, glutaraldehyde-perfused testes from men with low or high daily sperm production per g parenchyma were compared. Lobes of testicular parenchyma were teased from connective tissue septa, further fixed in osmium, and embedded such that the straight portions of tubules could be sectioned perpendicularly. Unstained 22 microns serial sections were sectioned optically with Nomarski optics. Paired photomicrographs of each tubular cross section were taken under a 40 x objective, and stages of the spermatogenic cycle were mapped by two observers using Clermont's criteria (Clermont, 1963). For comparison, numbers (1-6) were assigned randomly to the stages, the stages were plotted in two dimensions (length and circumference of tubule) as if the tubule were cut down its length and laid flat, and geometric centers were plotted for each stage. Geometric centers consecutive and/or non-consecutive stages appeared to form an angle down the length of the tubule. When considering helical patterns along the tubule, men with neither low nor high spermatogenic efficiency had a complete wave composed of all six consecutive stages. The helical pattern of geometric centers indicated only 2-4 consecutive stages when the actual values of stages were used or when random numbers were substituted for actual numerical value of stages. The number of consecutive stages in tubules from these men was not different from consecutiveness found when stages were assigned random numbers. Given that no complete wave was found, regardless of spermatogenic efficiency, and that the degree of consecutiveness of stages down a helical pattern in human seminiferous tubules could be generated from random numbers, the arrangement of stages in human seminiferous tubules may simply be a random occurrence.

Analysis of Variance↗