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Biomedical subjects

L W Johnson

Publications and source records attributed to L W Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Laparoscopic ovariectomy in two standing llamas.

Laparoscopic ovariectomy was performed in 2 llamas that were sedated but remained standing, avoiding possible complications associated with general anesthesia. All incisions were made in the left paralumbar fossa. The only intraoperative complications encountered were difficulty in maneuvering the laparoscope ventral to the uterine body in 1 llama because of distension of the urinary bladder, and a tendency to lean on the sidebar of the stocks in the other llama. The only postoperative complication was subcutaneous emphysema, which could be minimized by suctioning excess CO2 from the abdomen at completion of surgery. Laparoscopic ovariectomy was successful in these llamas and allowed direct examination and manipulation of the ovaries even though llamas were standing during surgery.

Anesthesia, Local↗
PubMed1998

Characterization of plasma immunoglobulin G concentrations of llamas.

OBJECTIVE: To develop appropriate reference ranges for plasma IgG concentrations of llamas. ANIMALS: 643 llamas on 5 farms. PROCEDURE: Plasma IgG concentration was measured by using a single radial immunodiffusion assay kit. Farm of origin, age, body condition score, and sex were recorded for each llama. The effect of each factor on plasma IgG concentration was evaluated separately, using ANOVA; the association between age and IgG concentration was evaluated, using linear regression. Multivariable regression models were developed to examine concurrent effects of age, sex, body condition score, farm, and various interactions on IgG concentration. RESULTS: The IgG concentrations were between 127 and 3,969 mg/dl. In llamas < 12 months old, farm of origin accounted for 29% of variability for IgG concentration. Reference range for plasma IgG concentrations in llamas < 12 months old was 391 to 2,357 mg/dl; for llamas > 12 but < 28 months old was 771 to 2,796 mg/dl; and for llamas > 28 months old was 570 to 3,264 mg/dl. These ranges were applicable only for the kit used in this study. CONCLUSIONS: Healthy llamas have a wide range of IgG concentrations. Determinants of IgG concentration are multifactorial, and their importance varies with age of the llamas. CLINICAL IMPLICATIONS: The wide range of IgG concentrations observed in healthy llamas and the influence that age and farm may have on IgG concentrations indicate that a result for one specific llama should be interpreted in relation to those of its herdmates.

Aging↗
PubMed1997

Surgical and nonsurgical correction of uterine torsion in New World camelids: 20 cases (1990-1996).

OBJECTIVE: To report clinical findings for New World comelids with uterine torsion and to compare results of 3 methods of correction. DESIGN: Retrospective case series. ANIMALS: 11 llamas and 3 alpacas with 20 uterine torsions. PROCEDURE: Information concerning history, clinical signs, management, and postpartum complications was retrieved from medical records. Information concerning subsequent reproductive performance was obtained by telephone interview of owners. RESULTS: Uterine torsion was corrected by celiotomy (n = 7); transvaginal manipulation (5), or rolling the dam (8). Direction of 19 of 20 torsions was clockwise when viewed from the rear. Retention of fetal membranes was reported for 5 camelids that underwent celiotomy, but was not reported in camelids after nonsurgical correction. The uterus prolapsed in 1 llama that underwent celiotomy and in another that underwent the rolling technique. Although 2 camelids that underwent celiotomy subsequently failed to conceive, all camelids treated by nonsurgical techniques conceived. CLINICAL IMPLICATIONS: Uterine torsion in camelids may be diagnosed by methods similar to those used in cattle. Surgical and nonsurgical methods can be used to correct torsion, and postpartum complications are rare when torsion is corrected by a nonsurgical method.

Abdomen↗
PubMed1997

Coronary angioplasty volume-outcome relationships for hospitals and cardiologists.

OBJECTIVE: To assess the relationship between each of 2 provider volume measures (annual hospital volume and annual cardiologist volume) for percutaneous transluminal coronary angioplasty (PTCA) and 2 outcomes of PTCA (in-hospital mortality and same-stay coronary artery bypass graft [CABG] surgery). DESIGN: Cohort study, using data from January 1, 1991, through December 31, 1994, from the Coronary Angioplasty Reporting System of the New York State Department of Health. SETTING: Thirty-one hospitals in New York State in which PTCA was performed during 1991-1994. PATIENTS: All 62670 patients discharged after undergoing PTCA in these hospitals during 1991-1994. MAIN OUTCOME MEASURES: Rates of in-hospital mortality and CABG surgery during the same stay as the PTCA. RESULTS: The overall in-hospital mortality rate for patients undergoing PTCA in New York during 1991-1994 was 0.90%, and the same-stay CABG surgery rate was 3.43%. Patients undergoing PTCA in hospitals with annual PTCA volumes less than 600 experienced a significantly higher risk-adjusted in-hospital mortality rate of 0.96% (95% confidence interval [CI], 0.91%-1.01%) and risk-adjusted same-stay CABG surgery rate of 3.92% (95% CI, 3.76%-4.08%). Patients undergoing PTCA by cardiologists with annual PTCA volumes less than 75 had mortality rates of 1.03% (95% CI, 0.91%-1.17%) and same-stay CABG surgery rates of 3.93% (95% CI, 3.65%-4.24%); both of these rates were also significantly higher than the rates for all patients. Also, same-stay CABG surgery rates for patients undergoing PTCA in hospitals with annual volumes of 600 to 999 performed by cardiologists with annual volumes of 75 to 174 (2.99%; 95% CI, 2.69%-3.31 %) and 175 or more (2.84%; 95% CI, 2.57%-3.14%) were significantly lower than the overall statewide rate (3.43%). CONCLUSIONS: In New York State, both hospital PTCA volume and cardiologist PTCA volume are significantly inversely related to in-hospital mortality rate and same-stay CABG surgery rate for patients undergoing PTCA.

Angioplasty, Balloon, Coronary↗
PubMed1997

The distribution of strain in the human cornea.

Experimental data on the mechanics of human cornea is meager and sometimes flawed. Moreover, questions regarding the correct material symmetry and the role of the fibrous microstructure are usually glossed over when mechanical models of the cornea and corneal shape changing procedures are presented. Accordingly, the deformation of 14 intact human corneas was measured for five pressures in the physiologic range (0, 5, 10, 25 and 45 cmH2O) by tracking small, self-adherent particles placed on their anterior surfaces. The meridional strains, calculated in five regions assuming axisymmetric deformation, are small; the average strain in the apical region being 1.14% at 45 cmH2O. Results also indicate that the strain distribution is unexpectedly nonuniform with statistically significant (p < 0.01, typical) variations between regions and a minimum occurring approximately half-way between apex and limbus. To better understand these results, a finite-element model (FEM) of the cornea was constructed and used to simulate the experiment. The heterogeneous model shows that our data may reflect the changing fiber orientation along a meridian suggested in the literature. The implications of a link between microstructure and mechanics are discussed in light of clinical procedures, such as radial keratotomy, the outcomes of which are dependent on corneal mechanical properties.

Cornea↗
PubMed1997

Single site electronic spectra of free base porphin in an n-octane crystal at 5 K.

The single site fluorescence and excitation spectra of free base porphin in an n-octane crystal at 5 K are reported. The vibrational frequencies of the ground and excited states (Qx, Qy, and B bands) have been determined from the spectra. The Qx region is very similar to the previously reported results from supersonic jet expansion. However, the Qy region is quite different in the jet and mixed crystal: the crystal spectrum exhibits extensive vibronic coupling. The Soret band shows little vibronic structure.

Crystallization↗
PubMed1997

Mitochondria transfer into mouse ova by microinjection.

A method for mitochondria isolation and interspecific transfer of mitochondria was developed in mice. Mitochondria were isolated from Mus spretus liver samples for microinjection into fertilized ova obtained from superovulated M. musculus domesticus females. Electron microscopic observations of mitochondria preparations used for microinjection demonstrated intact mitochondrial vesicles with little microsomal contamination. Species-specific nested PCR primers complementary to sequence differences in the mitochondrial DNA D-loop region revealed high rates of successful transfer of foreign mitochondria after isolation and injection into zygotes cultured through the blastocyst stage of embryonic development. Of 217 zygotes, 67 survived mitochondria injection and 23 out of 37 zygotes developed were at the blastocyst-stage of embryonic development after 4.5 days of in vitro culture. All 23 of these blastocysts contained detectable levels of foreign mitochondria. These results represent an initial step in developing a model system to study mitochondrial dynamics and development of therapeutic strategies for human metabolic diseases affected by aberrations in mitochondrial function or mutation.

Animals↗
PubMed1997

Effect of NG-nitro-L-arginine-methyl-ester on cardiopulmonary function and biosynthesis of cyclooxygenase products during porcine endotoxemia.

OBJECTIVE: To determine if inhibition of nitric oxide synthase with NG-nitro-L-arginine-methyl-ester (L-NAME) potentiates endotoxin-induced cardiopulmonary dysfunction and release of cyclooxygenase products in a porcine model of endotoxemia. DESIGN: Prospective, multiple group, controlled experimental study. SETTING: Physiologic research laboratory at a veterinary medicine college. SUBJECTS: Fifty-seven domestic pigs (mean 28.7 +/- 0.8 [SEM] kg). INTERVENTIONS: Pentobarbital-anesthetized pigs were intubated and mechanically ventilated to normocapnia with room air. A ther-modilution cardiac output catheter was advanced into the pulmonary artery. Additional catheters were inserted into the jugular and femoral veins and femoral artery. The pigs received the following infusions: saline (control, n = 5); L-NAME (0.1, 0.5, 2.2, or 5.5 mg/ kg/hr, from -0.5 to 2 hrs, n = 16); Escherichia coli endotoxin (5 micrograms/ kg from 0 to 1 hr followed by 2 micrograms/kg from 1 to 2 hrs, i.v., n = 14); L-NAME plus endotoxin (n = 9); indomethacin plus endotoxin (n = 6); or L-NAME indomethacin plus endotoxin (n = 7). MEASUREMENTS AND MAIN RESULTS: L-NAME significantly (p < .05) worsened endotoxin-induced hypoxemia and enhanced the increases in pulmonary vascular resistance index and systemic vascular resistance index at 30 to 60 mins. Endotoxin increased (p < .05) plasma concentrations of thromboxane B2 by seven- to eight-fold at 30 to 120 mins and 6-keto-prostaglandin F1 alpha by 16- to 24-fold at 60 to 120 mins. L-NAME enhanced (additive effect) endotoxin-induced increases in plasma concentrations of thromboxane B2 (60 mins) and significantly (p < .05) potentiated the increases in 6-keto-prostaglandin F1 alpha (120 mins). At 120 mins of endotoxemia, indomethacin (cyclooxygenase inhibitor) plus L-NAME markedly increased (p < .05, synergistic effect) systemic vascular resistance index compared with endotoxemic pigs pretreated with either L-NAME or indomethacin. CONCLUSIONS: During endotoxemia, inhibition of nitric oxide synthase with L-NAME may be deleterious to cardiopulmonary function, as evidence by potentiation of endotoxin-induced systemic and pulmonary vasoconstriction, impairment of gas exchange, and enhanced biosynthesis of cyclooxygenase products. Moreover, during endotoxemia, the concomitant inhibition of two important vasodilators (i.e., nitric oxide and prostacyclin) is associated with a potentiated (p < .05) increase in systemic vascular resistance index.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Molecular characterization of major histocompatibility complex (B) haplotypes in broiler chickens.

In Leghorn (laying) chickens, susceptibility to a number of infectious diseases is strongly associated with the major histocompatibility (B) complex. Nucleotide sequence data have been published for six class I (B-F) alleles and for class II (B-L beta) alleles or isotypes from 17 Leghorn haplotypes. It is not known if classical B-L or B-F alleles in broilers are identical, at the sequence level, to any Leghorn alleles. This report describes molecular and immunogenetic characterization of two haplotypes from commercial broiler breeder chickens that were originally identified by serology as a single haplotype, but were differentiated serologically in the present work. The two haplotypes, designated BA4 and BA4variant, shared identical B-G restriction fragment length polymorphism patterns, but differed in one B-L beta fragment that cosegregated with the serological B haplotype. Furthermore, the nucleotide sequences of the highly variable exons of an expressed B-L beta II family gene and B-F gene from the two haplotypes were markedly different from each other. Both the B-L beta II family and B-F gene sequences from the BA4 haplotype were identical to the sequences obtained from the reference B21 haplotype in Leghorns; however, in the BA4 haplotype the B-L beta 21 and B-F21 alleles were in linkage with B-G alleles that were not G21. The nucleotide sequences from BA4variant were unique among the reported chicken B-L beta II family and B-F alleles.

Animals↗
PubMed1997

Influence of moderate haemodilution with fluosol or normal saline on carbaryl disposition in Sprague-Dawley rats.

In rats carbaryl undergoes extensive biotransformation involving both albumin-mediated hydrolysis and cytochrome P-450-mediated metabolism; studies have suggested that approximately one-half of a carbaryl dose is hydrolysed and one-half is metabolized. Fluosol is known to be an inducer of cytochrome P-450, and Fluosol haemodilution reduces plasma albumin concentrations. The disposition of carbaryl was, therefore, determined in rats for 72 h after 40 mL kg-1 haemodilution with Fluosol or normal saline (0.9% NaCl). Volumes of distribution were significantly reduced after saline haemodilution for 72 h but only at 48 h after Fluosol haemodilution. Fluosol and saline haemodilution had little influence on carbaryl total body clearance (CL). These results indicate that both hepatic and non-hepatic clearance pathways were not influenced by the haemodiluents or the haemodilution procedure.

Animals↗
PubMed1996

Optimization of embryo transfer protocols for mice.

The efficiency of ova transfer and subsequent survivability were explored in this study. The goals of the experiment were to 1) determine the minimum number of ova necessary for pregnancy maintenance, 2) ascertain if the number of zygotes used in ova transfer approaches or exceeds uterine capacity, and 3) establish if location of deposition of ova influences embryo survival. A total of 1647 pronuclear zygotes were transferred in groups of 1, 2, 4, 6, 15 or 25 on Day 1 of gestation either via the oviducal ampulla or ostium to 156 nulliparous ICR pseudopregnant female mice. Pregnancy status was determined on Day 12 or Day 19 of gestation. Results indicated that pregnancy rates were not significantly increased by transferring larger numbers of zygotes (P < 0.1504) and that beyond transfer of 15 zygotes, the progressive increase in fetal numbers per litter declined. However, on Day 19 of gestation, no definitive evidence of limitation of uterine capacity was obtained with the numbers of zygotes transferred (P < 0.0531), and the estimates of numbers of viable and resorbed fetuses differed when determinations were made on Day 12 versus Day 19 of gestation. Mean numbers of developed fetuses per recipient declined (P < 0.0001), whereas the number of resorptions (partially resorbed fetuses or resorption sites) increased (P < 0.0001) over this period, reflecting fetal loss in mid- to late-gestation and possibly the transient nature of resorptions prior to Day 12. Additionally, there was no difference in pregnancy outcome when transferring ova into the oviducal ostium or isthmus (P < 0.5256). Finally, these results illustrated that when large numbers of zygotes were transferred into the oviducal ampulla, equivalent numbers of ova eventually implanted in the uterus; however, proportionally more of them began resorption.

Journal Article↗
PubMed1996

Extensive coronary dissection caused by balloon rupture at high pressure during stent deployment.

A patient with severe stenosis of the right coronary artery underwent successful stent placement. During high pressure postdilatation, the balloon ruptured, causing an extensive proximal dissection of the right coronary artery managed with the deployment of several additional stents. Strategies aimed at avoiding or minimizing the consequences of high pressure balloon rupture are discussed.

Catheterization↗
PubMed1996

B-haplotype control of CD4/CD8 subsets and TCR V beta usage in chicken T lymphocytes.

The major histocompatibility (B) complex of the chicken contains genes similar to Class I (B-F) and Class II (B-L beta) genes in mammals, as well as a highly-polymorphic gene family (B-G) whose exact function is not known. Specific B-haplotypes are strongly associated with resistance to a number of infectious diseases, and with immune responses to soluble and cellular antigens. In mammals, Class I and Class II molecules control development of the T cell repertoire, including selection of CD4+ and CD8+ T cells. One study of chickens reported that low CD4:CD8 ratio was associated with the B4 haplotype, which shares expressed B-F/B-L genes with the B13 haplotype. In studies reported here, chickens of two haplotypes carried in the Auburn R line, B302 and B305 (which is B13-related), were evaluated for percentages of T cells expressing the CD4, CD8, CD3, TCR1, TCR2 and TCR3 antigens in peripheral blood lymphocytes (PBL), thymus, and spleen. These two haplotypes were chosen for comparison because they differ in resistance to Marek's disease (MD) and are closely-related in B-F and B-L genes by restriction fragment length polymorphism analyses. Homozygous birds of each B haplotype were produced from crosses of (B302 x B305)F1 sires and dams. PBL, thymocytes, and splenocytes from B302 homozygotes had higher CD4:CD8 ratios than B305 homozygotes. However, CD4:CD8 ratio differences could not be attributed to haplotype-controlled differences in V beta usage within CD4/CD8 subsets, as has been described for certain V beta families in mice and humans. These results indicate that thymic selection events involving CD4 and CD8 subsets and TCR V beta usage are controlled by a gene or genes closely-linked to the B-complex, which may or may not be Class I or Class II genes.

Animals↗
PubMed1995

Family physicians' views of the preventive services task force recommendations regarding nutritional counseling.

OBJECTIVE: To determine the level of agreement between family physicians and the nutritional counseling recommendations of the US Preventive Services Task Force. DESIGN: A survey was developed, tested, and mailed to a random nationwide sample of 500 family physicians. PARTICIPANTS: Active members of the American Academy of Family Physicians, Kansas City, Mo. Forty-nine percent of the physicians responded to the survey. MAIN OUTCOME MEASURE: The level of agreement between family physicians and the nutritional counseling recommendations of the US Preventive Services Task Force was determined through responses from 1 to 7 on a Likert scale, with a higher number indicating a greater level of agreement. RESULTS: A comparison of age, gender, and type of practice found that the sample did not significantly differ from the characteristics of the membership of the American Academy of Family Physicians. Seventy-five percent of the physicians agreed that clinicians should provide periodic counseling regarding the dietary intake of fat and cholesterol. Fifty percent or more of the physicians agreed with the other five recommendations, including providing periodic counseling about the dietary energy intake, the dietary intake of sodium, and exercise and referring patients to a registered dietitian. Gender and type of practice had a significant effect on the level of agreement with the recommendations. CONCLUSIONS: Generally, this sample of family physicians agreed with the US Preventive Services Task Force nutritional counseling recommendations. Family physicians seemed to be supportive of nutritional counseling during the periodic health examination, but further research is required to identify barriers to implementation.

Adult↗
PubMed1995

Prospective characterization of the clinicopathologic and immunologic features of an immunodeficiency syndrome affecting juvenile llamas.

The clinicopathologic and immunologic features of 15 llamas affected with juvenile llama immunodeficiency syndrome (JLIDS) are described. Healthy adult (n = 10) and juvenile (n = 10) llamas served as controls. JLIDS llamas were characterized by wasting, and clinically apparent, repeated infections were frequently observed. The median age at which a health problem was first perceived was 11.6 months. All 15 affected llamas died or were killed, and JLIDS was confirmed at necropsy. The median duration of illness was 3.5 months. Lymphocyte blastogenesis assays showed suppressed responses (particularly to Staphylococcus sp. Protein A) in JLIDS llamas. No evidence of retroviral infection was detected. Mild, normocytic, normochromic, non-regenerative anemia, low serum albumin concentration and low to low-normal globulin concentrations were typically found on initial clinical evaluation. Lymph node biopsies showed areas of paracortical depletion. All llamas affected with JLIDS had low serum IgG concentrations, pre-vaccination titers against Clostridium perfringens C and D toxoids of < or = 1:100, and no titer increase following vaccination.

Animals↗
PubMed1995

Comparison of two commercially available single radial immunodiffusion kits for quantitation of llama immunoglobulin G.

Immunoglobin G (IgG) quantitation was performed by a commercially available single radial immunodiffusion kit on 528 plasma samples obtained from llamas. Fifty samples encompassing the range of values obtained were selected for further evaluation. The IgG concentration of these samples was measured by a second commercially available single radial immunodiffusion kit and a sodium sulfite precipitation kit. gamma-Globulins also were measured. IgG values predicted by the single radial immunodiffusion kits were not in agreement. Failure to appreciate this lack of agreement could result in misinterpretation of a llama's IgG level derived from one kit when clinical guidelines established using the other kit are followed.

Animals↗
PubMed1995

Urinary indices in llamas fed different diets.

Indices of renal function and damage were measured in 12 healthy male adult llamas fed a diet of mixed alfalfa/grass hay (mixed hay) and water ad libitum. Using a collection bag fitted over the preputial area, urine samples were collected at 6, 12, and 24 hours. Serum samples were obtained concurrently to determine endogenous creatinine clearance (CL), total (TE) and fractional excretion (FE) of electrolytes (Na, K, Cl, P), electrolyte CL, urine and serum osmolality, urine enzyme activities (gamma-glutamyltransferase and N-acetyl-beta-D-glucosaminidase), and urine protein concentration. Urine production was quantified. Three months later, 10 of the 12 llamas were fed a grass hay diet and water ad libitum. Similar samples were obtained, and similar measurements were made. Urine production was higher when the llamas were fed the mixed hay diet. Total urine volume for llamas fed mixed hay ranged from 628 to 1,760 ml/24 h, with a median of 1,307.5 ml/24h, compared with a range of 620 to 1,380 ml/24 h and a median of 927.50 ml/24h for llamas fed grass hay. Median urine osmolality was higher in llamas fed mixed hay (1,906 mOsm/kg of body weight, with a range of 1,237 to 2,529 mOsm/kg), compared with llamas fed grass hay (1,666 mOsm/kg with a range of 1,163 to 2,044 mOsm/kg). Creatinine CL did not vary significantly over time for either diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗