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Biomedical subjects

L Bowen

Publications and source records attributed to L Bowen.

At least 19 recordsLinked to original sources
PubMed2006

MHC gene configuration variation in geographically disparate populations of California sea lions (Zalophus californianus).

Major histocompatibility complex (MHC) class II DRB genotypes were examined in two geographically isolated populations of California sea lions (Zalophus californianus) (Gulf of California and California coastal Pacific Ocean). Genomic DNA from 227 California sea lions was examined using eight sequence-specific primer (SSP) pairs flanking the putative peptide-binding site. A total of 40 different Zaca-DRB genotype configurations were identified among the 227 individuals. Using SSP-PCR, significant differences were found between coastal California and Gulf of California Zalophus populations in numbers of DRB sequences per individual and configuration of sequences within individuals. Additionally, unique local patterns of MHC diversity were identified among the Midriff Island animals. These population differences are consistent with either ecologically distinct patterns of selection pressures and/or geographical isolation. The consequences of these partitioned MHC configurations at the population level are as yet unknown; however, the worldwide increase in emerging marine diseases lends urgency to their examination.

California↗
PubMed2006

Expressed MHC class II genes in sea otters (Enhydra lutris) from geographically disparate populations.

The major histocompatibility complex (MHC) is central to maintaining the immunologic vigor of individuals and populations. Classical MHC class II genes were targeted for partial sequencing in sea otters (Enhydra lutris) from populations in California, Washington, and Alaska. Sequences derived from sea otter peripheral blood leukocyte mRNAs were similar to those classified as DQA, DQB, DRA, and DRB in other species. Comparisons of the derived amino acid compositions supported the classification of these as functional molecules from at least one DQA, DQB, and DRA locus and at least two DRB loci. While limited in scope, phylogenetic analysis of the DRB peptide-binding region suggested the possible existence of distinct clades demarcated by geographic region. These preliminary findings support the need for additional MHC gene sequencing and expansion to a comprehensive study targeting additional otters.

Alaska↗
PubMed2001

Ectoparasites of the island fox on Santa Cruz Island.

The ectoparasite fauna for island foxes (Urocyon littoralis) on Santa Cruz Island (California, USA) in April (wet season) and September (dry season) 1998 was evaluated. Three taxa of ectoparasites were identified. These were fleas (Pulex irritans), lice (Neotrichodectes mephitidis), and ticks (Ixodes pacificus). Ectoparasite abundances varied seasonally. Typical of insular endemic species, island foxes may be especially vulnerable to the introduction of novel disease organisms and their vectors.

Animal Diseases↗
PubMed2000

Hematology and serum chemistry of the island fox on Santa Cruz Island.

Serum and hematologic biochemistry values for island foxes (Urocyon littoralis) on Santa Cruz Island (California, USA) in April (wet season) and September (dry season) 1998 were evaluated. Serum chemistry of island foxes generally varied seasonally; 10 (40%) of the 25 serum characteristics were higher in the wet season, and three (12%) of the 25 serum characteristics were higher in the dry season. No hematologic parameters varied between seasons, although some measures varied between sexes. Blood analytes also varied with age; fox pups had higher values than adults for one hematologic and four serum parameters, whereas adult foxes had higher values for five hematologic characteristics. The information on blood chemistry provides baseline data useful in the monitoring of this threatened insular endemic carnivore.

Aging↗
PubMed1998

Regulation of periodontal ligament cell functions by interleukin-1beta.

Periodontal ligament (PDL) cells maintain the attachment of the tooth to alveolar bone. These cells reside at a site in which they are challenged frequently by bacterial products and proinflammatory cytokines, such as interleukin-1beta (IL-1beta), during infections. In our initial studies we observed that IL-1beta down-regulates the osteoblast-like characteristics of PDL cells in vitro. Therefore, we examined the functional significance of the loss of the PDL cell's osteoblast-like characteristics during inflammation. In this report we show that, during inflammation, IL-1beta can modulate the phenotypic characteristics of PDL cells to a more functionally significant lipopolysaccharide (LPS)-responsive phenotype. In a healthy periodontium PDL cells exhibit an osteoblast-like phenotype and are unresponsive to gram-negative bacterial LPS. Treatment of PDL cells with IL-1beta inhibits the expression of their osteoblast-like characteristics, as assessed by the failure to express transforming growth factor beta1 (TGF-beta1) and proteins associated with mineralization, such as alkaline phosphatase and osteocalcin. As a consequence of this IL-1beta-induced phenotypic change, PDL cells become responsive to LPS and synthesize proinflammatory cytokines. The IL-1beta-induced phenotypic changes in PDL cells were transient, as removal of IL-1beta from PDL cell cultures resulted in reacquisition of their osteoblast-like characteristics and lack of LPS responsiveness. The IL-1beta-induced phenotypic changes occurred at concentrations that are frequently observed in tissue exudates during periodontal inflammation (0.05 to 5 ng/ml). The results suggest that, during inflammation in vivo, IL-1beta may modulate PDL cell functions, allowing PDL cells to participate directly in the disease process by assuming LPS responsiveness at the expense of their normal structural properties and functions.

Adult↗
PubMed1995

LPS responsiveness in periodontal ligament cells is regulated by tumor necrosis factor-alpha.

Gingival fibroblasts function as accessory immune cells and are capable of synthesizing cytokines in response to lipopolysaccharides (LPS) from Gram-negative microbes. Recently, we have isolated, cloned, and characterized two cell lines which exhibit characteristics of periodontal ligament (PDL) cells. In this report, we demonstrate that PDL cells showing osteoblast-like phenotype are not LPS-responsive cells. However, treatment of PDL cells with tumor necrosis factor-alpha (TNF-alpha) inhibits the expression of their osteoblast-like characteristics. As a consequence of this TNF-alpha-induced phenotypic change, PDL cells become LPS-responsive, i.e., synthesize several pro-inflammatory cytokines in response to LPS. These phenotypic changes occur at concentrations of TNF-alpha that are frequently observed in tissue exudates during periodontal inflammation, suggesting a physiological significance for these in vitro observations. It is of interest that TNF-alpha-induced phenotypic changes in PDL cells are transient, since removal of rhTNF-alpha from the supernatants of PDL cell cultures results in re-acquisition of the osteoblast-like characteristics and lack of LPS responsiveness of PDL cells. These results suggest that TNF-alpha, by regulating the PDL cell functions, may allow these cells to participate in the disease process as accessory immune cells at the expense of their structural properties.

Alkaline Phosphatase↗
PubMed1994

Optimal drug and behavior therapy for treatment-refractory schizophrenic patients.

Thirteen treatment-refractory schizophrenic patients (10 men and three women) who were receiving more than 50 mg/day of haloperidol and who had been hospitalized for more than 1 year successfully tolerated a mean dose reduction of 63% with consequent improvement in psychopathology and side effects. The addition of intensive behavior therapy to the optimal dose of haloperidol yielded further improvements in functional behavior, such as self-care and social interaction.

Adult↗
PubMed1993

Prediction of response to haloperidol dose reduction by Span of Apprehension measures for treatment-refractory schizophrenic patients.

Thirteen treatment-refractory schizophrenic patients participated in a haloperidol reduction study. Two of the subjects were unable to tolerate medication reduction. These subjects were comparable to the other patients in terms of initial clinical variables but were outliers on baseline accuracy and reaction time measures from the Span of Apprehension. The results suggest that aspects of basic visual processing and motor response speed may identify patients who require higher neuroleptic doses.

Adult↗
PubMed1993

Systematic dosage reduction in treatment-resistant schizophrenic patients.

Thirteen treatment-resistant, chronically institutionalized schizophrenic patients on high-dose neuroleptic (the equivalent of at least 50 mg of haloperidol (HPL) daily) were transferred to a special research ward for a trial of systematic dosage reduction. In these 13 patients, it was possible to reduce the dose of HPL from 63.1 mg/day (SD +/- 12.5, range = 50-80 mg/day) to 23.1 mg/day (SD +/- 16.3, range = 0-65 mg/day) over a mean period of 32 weeks (SD +/- 9.6, range = 15-46 weeks). Their total Brief Psychiatric Rating Scale (BPRS) scores were improved (p = .04), they definitely experienced fewer extrapyramidal side effects (p = .01), and 6 of the patients showed global improvement. On several behavioral rating scales there was, if anything, an improvement in negativistic behavior. The substantial dosage reduction was paralleled by a comparable drop in plasma levels. HPL plasma levels at baseline were 38.8 ng/mL (SD +/- 17.8, range = 21.5-69.5 ng/mL) and at the lowest effective dose were 12.4 ng/mL (SD +/- 10.3, range = 0-43.4 ng/mL).

Adult↗
PubMed1992

Optimal drug and behavior therapy for treatment-refractory institutionalized schizophrenics.

Institutionalized persons with a deteriorating form of schizophrenia that was refractory to neuroleptic medication were titrated downward in their haloperidol dose. Based on ratings of their clinical status, an optimal dose was reached that was an average 66 percent reduction from their initial levels. Patients then participated in a personalized, intensive behavior therapy program to remediate their extreme, persisting deficits and disturbances in behavior.

Adult↗
PubMed1991

The effect of CP 68,722, a thiozolidinedione derivative, on insulin sensitivity in lean and obese Zucker rats.

The effect of a new drug (CP 68,722, Pfizer) on parameters of insulin sensitivity in an established insulin-resistant animal model was examined. Rates of hepatic glucose production (HGP) and peripheral glucose uptake in obese Zucker (fa/fa) rats treated with a 10-day course of the medication using a two-step (2 and 10 mU/kg/min) euglycemic hyperinsulinemic clamp technique were measured. In addition, changes in substrate concentrations after drug treatment were examined. Basal HGP rates were similar in the lean versus the obese animals (37 +/- 3 v 39 +/- 3 mumol/kg/min); however, the obese animals had impaired insulin-induced suppression of HGP at both 2 mU/kg/min (36 +/- 3 v 23 +/- 4 mumol/kg/min) and 10 mU/kg/min (18 +/- 5 v 2 +/- 1 mumol/kg/min). Insulin stimulation of glucose disposal was also defective in the obese animals (37 +/- 2 v 88 +/- 7 mumol/kg/min at 2 mU/kg/min and 98 +/- 9 v 219 +/- 18 mumol/kg/min at 10 mU/kg/min). In addition, obese animals had elevated free fatty acid (FFA) and ketone levels, both of which were resistant to insulin-induced suppression. After drug treatment, few alterations in glucose or lipid metabolism were found in the lean animals. In the obese animals, insulin suppression of HGP was normalized during the higher insulin infusion rate (0 v 18 +/- 5 mumol/kg/min at 10 mU/kg/min), and peripheral glucose disposal was enhanced at both steps of the insulin clamp (54 +/- 4 v 37 +/- 2 mumol/kg/min at 2 mU/kg/min and 134 +/- 12 v 98 +/- 9 mumol/kg/min at 10 mU/kg/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Metabolic effects of IGF-I and insulin in spontaneously diabetic BB/w rats.

To examine the influence of insulin-dependent diabetes on the metabolic response to insulin-like growth factor I (IGF-I), awake chronically catheterized diabetic and nondiabetic BB/w rats received IGF-I (5 micrograms.kg-1.min-1) or insulin (2 mU.kg-1.min-1) for 2 h while maintaining euglycemia. In nondiabetic rats, IGF-I and insulin produced similar twofold increases in glucose uptake, but insulin was more effective in reducing hepatic glucose production (90 +/- 15 vs. 5 +/- 11%; P less than 0.001) and beta-hydroxybutyrate levels (94 +/- 1 vs. 19 +/- 6%; P less than 0.001). In diabetic rats, insulin-stimulated glucose uptake was impaired (8.5 +/- 0.9 vs. 11.5 +/- 0.9 mg.kg-1.min-1 in nondiabetics; P less than 0.05). In contrast, IGF-I-stimulated glucose uptake was identical in diabetic and nondiabetic rats. Furthermore, IGF-I suppressed glucose production by 73% (P less than 0.01) and caused a greater lowering of beta-hydroxybutyrate levels (from 2.9 +/- 0.8 to 0.8 +/- 0.3 mumol/l) in diabetic rats. We conclude that 1) the capacity of IGF-I infusion to stimulate glucose uptake is maintained in spontaneously diabetic BB rats that are insulin resistant, and 2) IGF-I infusion suppresses elevated glucose production rates and plasma ketone concentrations in diabetic rats but is relatively ineffective in nondiabetic rats. Thus the metabolic responses to infused IGF-I do not appear to be diminished in diabetic rats with impaired responses to insulin.

Amino Acids↗
PubMed1990

Successful behavioral treatment of polydipsia in a schizophrenic patient.

Behavioral treatment of a 35 year old female with chronic schizophrenia and water intoxication with seizures was conducted on an inpatient psychiatric unit. Treatment included frequent daily weights, restricted fluid intake, positive reinforcement for program compliance, and time-out from reinforcement following significant weight gain or other specified program violations. The final 6 months of the 30 month treatment program were a maintenance phase during which most contingencies were faded and all fluid restrictions were removed. There was no reported recurrence of polydipsia after 18 months of community placement.

Adult↗