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Biomedical subjects

R C Baker

Publications and source records attributed to R C Baker.

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

Weight control during the holidays: highly consistent self-monitoring as a potentially useful coping mechanism.

The study examined the extent to which trait self-monitoring (the systematic observation and recording of target behaviors) was related to weight control during the high-risk holiday season. The participants (32 women, 6 men) averaged 223.1 lbs (101.41 kg), 57.2% overweight, 50.2 weeks of participation, and 21.3 lbs (9.68 kg) lost at the beginning of the study. Consistency of self-monitoring and weight changes were assessed for 3 holiday versus 7 nonholiday weeks. Analyses of variance (Consistency of Self-Monitoring Groups x Holiday/Nonholiday Weeks) revealed that participants gained 500% more weight per week during holiday compared with nonholiday weeks. Only participants in the most consistent self-monitoring quartile averaged any weight loss over the 10 weeks of the study and during the holiday weeks.

Adaptation, Psychological↗
PubMed1997

Negative and positive regulation of astrocyte DNA synthesis by ethanol.

Ethanol suppression of astrocyte mitogenesis is well recognized but ethanol, under some conditions, has also been shown to stimulate astrocyte proliferation. This study addressed the role of protein kinase C and other mitogenic factors as mechanisms responsible for the bidirectional effects of ethanol on astrocyte DNA synthesis. Ethanol treatment inhibited astrocyte DNA synthesis both at 4 hr (short term) and 24 hr (long term) in serum free medium. In contrast, when the medium contained serum, ethanol was less effective in inhibiting DNA synthesis at 4 hr and treatment with ethanol for 24 hr increased DNA synthesis. Protein kinase C activity was increased in cells treated with ethanol for either 4 or 24 hr. Ethanol inhibition of DNA synthesis in serum free medium was not reversed by down regulating protein kinase C. In contrast, downregulating protein kinase C activity by continuous treatment with phorbol myristic acetate partially reversed the effect ethanol had on DNA synthesis. Also, directly inhibiting protein kinase C with H-7 in cells maintained and treated in the presence of serum abolished the stimulatory effect ethanol had on DNA synthesis. It appears that the negative regulation of astrocyte DNA synthesis by ethanol occurs by protein kinase C and serum independent mechanisms whereas adaptive or stimulatory effects of ethanol on astrocyte DNA synthesis requires the interaction of protein kinase C with other factors present in serum.

Animals↗
PubMed1997

Ethanol-induced apoptosis in human HL-60 cells.

The mechanisms responsible for aberrant immune function associated with chronic ethanol use remain obscure, but a decrease in monocyte numbers is often reported for individuals who chronically abuse ethanol. We investigated, using human HL-60 promyelocytic cell line, the possibility that ethanol induces apoptosis which contributes to decreased monocyte numbers. Characteristic features of apoptosis were observed 4 days after ethanol treatment, as documented by increased DNA fragmentation; enhanced expression of phosphatidylserine, an early marker of apoptosis; and the appearance of a hypodiploid apoptotic cell population identified by flow cytometry analysis of the cell cycle. Treatment with the protein kinase C inhibitor, GF 109203X, potentiated ethanol-induced apoptosis. Direct induction of human HL-60 cell apoptosis by ethanol and potentiation of ethanol-induced apoptosis by inhibiting protein kinase C provides a partial explanation for the cytotoxic effects of ethanol on hematopoietic progenitor cells and establishes a link between inhibiting protein kinase C activity and ethanol-induced apoptosis.

Apoptosis↗
PubMed1997

The effects of pretraining on group psychotherapy for incest-related issues.

The effects of written, cognitive pretraining on self-reported self-disclosure and cohesion in group psychotherapy were studied. Subjects were members of time-limited psychotherapy groups that focused on incest-related issues. The experimental groups were given written cognitive pretraining designed to increase self-reported self-disclosure and cohesion. The control groups received general group information. Subjects in the pretrained groups reported higher levels of self-perceived self-disclosure than the control groups after sessions 4 (p = 0.003) and 8 (p = 0.003). Self-reported self-disclosure did not increase over time for pretrained or nonpretrained subjects. Cohesion did not differ across groups, but increased over time for experimental subjects (p = .008), and not for control subjects.

Adult↗
PubMed1997

The relationship of homophobia to intimacy in heterosexual men.

Interpersonal intimacy is more difficult to achieve for American men than women. Research has shown that men disclose less, have fewer close friendships, and are viewed by their wives as low in intimacy. Among the barriers to intimacy among men, Tognoli (1980) suggested that homophobia is the most powerful. The present study tested this idea by asking men to disclose a personal secret to either a male confidant, a female confidante, or by writing the secret. It was expected that the presence of a male confidant would stimulate homophobic feelings and inhibit disclosure, while the other two conditions would result in more personal disclosure. A correlation between intimacy of disclosure and level of homophobia was also expected. Subjects were 75 heterosexual men, 31 to 50 years of age, randomly assigned to one of the three conditions. They also completed the Miller Social Intimacy Scale, the Jourard Self-Disclosure Questionnaire, the Index of Homophobia, and the Marlowe-Crowne Social Desirability Scale. Results showed that homophobia was inversely related to level of social intimacy. There was some indication that homophobia does relate to less intimate disclosure to other males. Thus this study found some support for the idea that homophobia is an obstacle to intimacy for men.

Adult↗
PubMed1997

Phosphorylated zidovudine concentrations in mononuclear cells in pediatric patients with human immunodeficiency virus infections.

PURPOSE: The efficacy of zidovudine (ZDV) in patients with HIV-1 infection may decrease over time due to its decreased activation. The objectives of this study were to determine ZDV concentrations in plasma, active phosphorylated zidovudine (pZDV) concentrations in mononuclear cells, and assess the markers of immune function and drug toxicity during extended therapy. METHODS: Pediatric patients (aged 3 months to 18 years) with HIV-1-infection were enrolled in the study. For each patient, one blood sample was collected at each of eight routine visits to measure plasma ZDV and ZDV concentrations by a radioimmunoassay. Data including demographic information, immunological markers (CD2+, CD3+, CD4+, CD5+/19+, CD8+, CD16+, CD19+, CD38+/8+ lymphocytes), hematologic function (absolute neutrophil count, white blood cell with differential, hemoglobin, and red blood cell count), concurrent medications, and dosage regimens were obtained. RESULTS: The data from 13 patients were as follows: age: 2-18 years; range of ZDV dose: 76-238 mg/m2, total ZDV daily dosage: 264-720 mg/m2; duration of ZDV therapy prior to study: 1 to 37 months; time in study: 180-394 days; plasma ZDV concentration range: 5-1021 ng/ml; and pZDV concentration range: 0-5.382 pmol/10(6) cells. Both plasma ZDV and intracellular pZDV concentrations had a marked inter- and intrapatient variability. The pZDV concentrations decreased significantly over time in one pediatric patient (p < 0.05), tended to decrease but not significantly in three patients, and no decrease was detected in nine patients due to high variability. In our population, neither immunological nor drug toxicity markers changed over time. CONCLUSIONS: Marked inter- and intrapatient variability in pZDV concentrations was observed. The ability to phosphorylate ZDV, however, did not appear to change significantly in 12 of 13 pediatric patients with HIV-1 infection during the study period of 6-13 months.

Adolescent↗
PubMed1997

Effect of exogenous GM1 on ethanol sensitivity in selectively bred mouse lines.

Ethanol sensitive long-sleep (LS) and ethanol resistant short-sleep (SS) mice are lines that have been genetically selected for differential central nervous system sensitivities to the hypnotic effect of ethanol. Because they were genetically selected only for differences in sensitivity to ethanol hypnosis, biochemical and physiological differences between them are likely related to their differential ethanol sensitivity. The synaptosomal and whole brain concentration of GM1 ganglioside was previously shown to differ significantly between the lines. Further, GM1 alters membrane responses to ethanol, including a differential effect on LS and SS synaptosomal membrane disordering. Therefore, GM1 was administered intracerebroventricularly (i.c.v.) with micro-osmotic pumps, to partially bypass the blood-brain barrier and to test its effect on CNS sensitivity to ethanol hypnosis in LS and SS mice. In the first experiment, 3 days' infusion of GM1 (20 micrograms/microliters, 24 microliters/day), saline control and treated LS and SS mice were tested for both regaining of the righting reflex and waking brain ethanol concentration. Incorporation of 3H-GM1 into brain membranes was verified by scintillation spectroscopy. GM1 did not alter ethanol sensitivity or brain ethanol concentration at time of waking in LS mice. Conversely, SS mice treated with GM1 were significantly more sensitive to ethanol hypnosis than saline controls as measured by the time to regain the righting reflex ("sleep time") and waking brain ethanol concentrations. In the second experiment, GM1-treated SS mice were again significantly more sensitive to ethanol hypnosis than saline controls. GM1 incorporation into the contralateral and ipsilateral cerebral hemispheres was determined by high-performance liquid chromatography.

Animals↗
PubMed1996

Effects of inhalation anesthetics of Kainate-induced glutamate release from cerebellar granule cells.

The mechanisms of inhalation anesthesia may include inhibiting non NMDA excitatory amino acid neurotransmission. This possibility was addressed by measuring the effect of three anesthetics at clinically relevant concentration on kainate-induced glutamate release from cerebellar granule cells. Cerebellar granule cells were obtained from 8-day-old SD rats and maintained in vitro for 9-14 days. Medium glutamate concentrations were measured by HPLC after 90 minutes incubation with kainate or NMDA. Inhalation anesthetics were introduced by holding the cells under a continuous flow of air/anesthetic mixtures. All anesthetics tested did not effect NMDA-induced glutamate release. Halothane (1 MAC), isoflurane (1 MAC) inhibited kainate-induced glutamate release from the cultured cells whereas enflurane (1 MAC) had no effect on kainate-induced glutamate release. The difference between enflurane and the other anesthetics tested suggests that anesthesia is dependent on more than one process and the extent at which each function is perturbed is dependent on the specific anesthetic used. Halothane inhibition of kainate-induced glutamate release was not reversible by increasing kainate concentration, indicating halothane does not directly compete with kainate at its receptor.

Anesthetics, Inhalation↗
PubMed1996

Neurodevelopmental outcome of infants with viral meningitis in the first three months of life.

We prospectively evaluated the neurodevelopmental outcome of infants with documented viral meningitis to determine (1) whether deficits in physical growth, development, speech and language, hearing, or intelligence occur; and (2) if so, at what age these deficits can be detected. Sixteen infants with documented enteroviral meningitis under the age of 90 days and a control group of 13 patients matched for age, race, sex, and socioeconomic status were followed up prospectively for 3 years with annual evaluations, which included a developmental evaluation by a pediatric developmentalist, articulation and language tests by a speech-language pathologist (Sequenced Inventory of Communication Development, Receptive-Expressive Emergent Language Scale (REEL), Preschool Language Scale (PLS), Revised Peabody Picture Vocabulary Test (PPVT-R), Photo Articulation Test, audiometric screening), and intelligence tests by a psychometrist (Bayley Scales of Infant Development [BSID] and Stanford-Binet). No deficits were demonstrated in growth, development, hearing, BSID, articulation, and expressive language. Subtle but significant (P < 0.05) deficits were documented in the study group compared with the control group in the receptive component of the REEL, all subsections of the PLS, the PPVT-R, and the verbal comprehension/language-processing section (Factor II) of the Stanford-Binet. These differences could be reliably detected by 3 years of age. We conclude that viral meningitis in young infants may cause subtle deficits in language skills, particularly receptive language. We recommend that children who have had enteroviral meningitis during early infancy be monitored carefully for language development and, perhaps, receive increased language stimulation in the home prior to school entry in order to optimize their learning potential.

Analysis of Variance↗
PubMed1996

Attitudes and practices of physicians caring for HIV-infected children.

OBJECTIVE: The objective of our study was to describe the practices and attitudes of physicians who manage children with HIV infection. METHODS: A 32-question survey was sent to the medical directors of 256 pediatric HIV centers. RESULTS: Fifty-four percent of centers responded. Seventy-two percent of practitioners had been involved in HIV-related care for more than 5 years. The most common subspecialities of respondents were infectious diseases (37%) and general pediatrics (28%). Although 65% of respondents found their HIV practice more stressful than their other responsibilities, the majority of physicians (65%) felt that their HIV-related responsibilities enhanced their careers. Sixty-eight percent had some concern about contracting HIV and 24% had been exposed to HIV by needle stick injury. Polymerase chain reaction and HIV culture were the main diagnostic tests used, 78 and 62%, respectively. Trimethoprim/sulfamethoxazole for prophylaxis against Pneumocystis carinii pneumonia and zidovudine therapy for primary HIV infection were the first line drugs used by almost all respondents. Only 9% were using intravenous immunoglobulin routinely. Fifty-two percent routinely advocated zidovudine for prophylaxis of HIV infection with needle stick injury. Eighty-three percent of those surveyed thought that all pregnant women should be tested for HIV and 88% advocated treating mother/infant pairs with zidovudine if the mother is HIV-infected. CONCLUSIONS: While HIV practitioners find their work stressful, the majority feel their careers are enhanced by their HIV-related work. There is agreement among most practitioners with regards to diagnostic tests, first-line drug therapies and the limited use of intravenous immunoglobulin. The vast majority of physicians advocate testing pregnant women for HIV infection and treating the mother/ infant pair with zidovudine if the mother is infected.

AIDS Serodiagnosis↗
PubMed1995

Comparison of 1% and 2.5% selenium sulfide in the treatment of tinea capitis.

OBJECTIVE: To determine whether an over-the-counter shampoo containing 1% selenium sulfide would have sporicidal activity equal to that of a 2.5% selenium sulfide prescription lotion in the adjunctive treatment of tinea capitis infection. DESIGN: Prospective randomized nonblinded clinical trial. SETTING: Outpatient clinics and emergency department of a children's hospital. PATIENTS: Fifty-four patients between the ages of 1 and 15 years with culture-proved tinea capitis infection caused by Trichophyton tonsurans enrolled during a 14-month period. METHODS: Patients were randomized to receive 2.5% selenium sulfide lotion, 1% selenium sulfide shampoo, or a bland, nonmedicated shampoo with which they were instructed to shampoo twice weekly. All received 15 mg/kg per day of griseofulvin. Dermatophyte cultures of the affected area of each patient's scalp were obtained on enrollment and every 2 weeks until a negative culture was obtained from a previously infected area. RESULTS: Survival data analysis demonstrated that both the 2.5% selenium sulfide and 1% selenium sulfide preparations were superior to the nonmedicated control shampoo in terms of the time required to eliminate shedding of viable spores. When compared with each other, there was no difference between the 2.5% selenium sulfide and 1% selenium sulfide preparations in time required to produce a negative culture. CONCLUSION: Commercially available 1% selenium sulfide shampoo is an equally effective yet less expensive alternative sporicidal therapy in the adjunctive treatment of tinea capitis infection.

Adolescent↗
PubMed1995

The effects of cognitive pretraining on cohesion and self-disclosure in small groups: an analog study.

This study examined the effects of written, cognitive pretraining on the development of cohesion and self-disclosure in interpersonal learning groups. Subjects in the experimental condition received a written introduction to the group experience, and subjects in the control condition received written information on the history of group psychotherapy. Results demonstrated that the experimental groups had a higher level of group cohesion than the control groups, p < .0001, but were not different on self-disclosure. The correlation between cohesion and self-disclosure was not statistically significant. The results were discussed as an extension of the empirical support for cognitive pretraining.

Adolescent↗
PubMed1995

L-glutamate-induced changes in intracellular calcium oscillation frequency through non-classical glutamate receptor binding in cultured rat myocardial cells.

The effects of L-glutamate, N-methyl-D-aspartate (NMDA), kainate (KA) and L-alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionate (AMPA) on intracellular Ca2+ oscillation frequency were studied in cultured rat myocardial cells. Ca2+ oscillations per minute were increased as compared to control by L-glutamate (100 microM) from 3.8 +/- 2.2 to 25.7 +/- 4.3 (p < 0.001) and the NMDA-receptor agonist, NMDA (100 microM), from 1.2 +/- 0.8 to 34.8 +/- 10.1 (p < 0.011). Increases over control frequency were also seen in response to the non-NMDA receptor agonists KA (100 microM) from 5.8 +/- 2.3 to 25.6 +/- 3.2 (p < 0.001) and AMPA (10 microM) from 3.8 +/- 1.2 to 13.3 +/- 1.8 (p < 0.001). The non-competitive NMDA receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK801) (10 microM), decreased the Ca2+ oscillation frequency induced by NMDA (100 microM from 36.8 +/- 12.2 to 7.2 +/- 7.2 (p < 0.05). (+/-)-2-Amino-7-phosphonoheptanoic acid (AP7), a competitive inhibitor at the NMDA receptor inhibited the increase in frequency induced by KA (100 microM) at all concentrations tested (0.1, 1.0, 10 and 100 microM). 6,7-Dinitroquinoxaline-2,3-dione (DNQX), a competitive inhibitor at non-NMDA receptors, also decreased the oscillation frequency elicited by KA (100 microM) from 35.4 +/- 9.4 to 28.2 +/- 9.8, 24.8 +/- 9.8 and 11 +/- 9.5 at concentrations of 0.1, 1.0 and 10 microM respectively. The peak amount of intracellular Ca2+ as expressed as the fluo 3 ratio, F/Frcst, was not increased by L-glutamate, NMDA or KA. These results suggest the presence of a novel glutamate receptor composed of both non-NMDA and NMDA subunits on cultured rat myocardial cells, and receptor stimulation leads to an increase in intracellular Ca2+ oscillation frequency.

Animals↗
PubMed1995

Genetic analysis of human immunodeficiency virus type 1 envelope V3 region isolates from mothers and infants after perinatal transmission.

The human immunodeficiency virus type 1 (HIV-1) sequences from variable region 3 (V3) of the envelope gene were analyzed from seven infected mother-infant pairs following perinatal transmission. The V3 region sequences directly derived from the DNA of the uncultured peripheral blood mononuclear cells from infected mothers displayed a heterogeneous population. In contrast, the infants' sequences were less diverse than those of their mothers. In addition, the sequences from the younger infants' peripheral blood mononuclear cell DNA were more homogeneous than the older infants' sequences. All infants' sequences were different but displayed patterns similar to those seen in their mothers. In the mother-infant pair sequences analyzed, a minor genotype or subtype found in the mothers predominated in their infants. The conserved N-linked glycosylation site proximal to the first cysteine of the V3 loop was absent only in one infant's sequence set and in some variants of two other infants' sequences. Furthermore, the HIV-1 sequences of the epidemiologically linked mother-infant pairs were closer than the sequences of epidemiologically unlinked individuals, suggesting that the sequence comparison of mother-infant pairs done in order to identify genetic variants transmitted from mother to infant could be performed even in older infants. There was no evidence for transmission of a major genotype or multiple genotypes from mother to infant. In conclusion, a minor genotype of maternal virus is transmitted to the infants, and this finding could be useful in developing strategies to prevent maternal transmission of HIV-1 by means of perinatal interventions.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Resting energy expenditure and body composition in pediatric HIV infection.

One of the most striking features of HIV disease is the "wasting syndrome" or failure to thrive. Eighty percent of all perinatally HIV-infected children fail to grow normally. OBJECTIVE. Because severe malnutrition increases the morbidity of HIV infection and may shorten the already limited life expectancy of this population, we assessed resting energy needs, body composition, and nutrient intake in nine children perinatally HIV-infected, age 4 months to 4 years. DESIGN. Subjects were studied using measurements of resting energy expenditure (REE) by indirect calorimetry, body composition measurements by dual-energy X-ray absorptiometry (DEXA) and skinfolds, nutrient intake analysis by 24-hour recall, and serum protein levels. The HIV-infected children were free of secondary opportunistic infection at the time of the study. Subjects were reevaluated within the following year. RESULTS. REE correlated well (r = .856) with the predicted value from the World Health Organization (WHO) equation for basal energy expenditure. Measurement of percent body fat by skinfolds correlated well with DEXA percent body fat (r = .61). There was no significant difference between body fat assessed from skinfolds compared to published age-matched standards. All subjects met their recommended dietary allowance (RDA) for calories and protein. All subjects had adequate visceral protein stores for age. CONCLUSION. Perinatally infected children were not hypermetabolic when not secondarily infected and were able to maintain normal growth with the provision of adequate nutrition.

Basal Metabolism↗
PubMed1994

Effect of pentobarbital and gaseous anesthetics on rats selectively bred for ethanol sensitivity.

Rats have been genetically selected to have a differential hypnotic response to an acute injection of ethanol. These high alcohol sensitive (HAS) and low alcohol sensitive (LAS) rats were used to investigate commonalities of the mechanism of action of several gaseous anesthetics, pentobarbital and ethanol. Similar studies have been carried out extensively with mouse lines also differentially sensitive to ethanol (short- and long-sleep mice). Like the mice, the rats are also differentially sensitive to the two gaseous anesthetics, enflurane and isoflurane. However, in contrast to results with these mice, we find that the HAS and LAS rats are differentially sensitive to halothane and pentobarbital in the same direction as their sensitivity to ethanol. In other studies, the rats also have been found to be differentially sensitive to phenobarbital as are SS and LS mice. These results show that, by the use of these anesthetics in combination with selectively bred rodent lines, many new opportunities for dissecting the molecular mechanisms of anesthetic agents present themselves.

Anesthetics↗
PubMed1994

Psychological correlates of codependency in women.

This study examined several potential psychological correlates of codependency to determine the parameters and feasibility of the codependency construct. Subjects were 171 adult female volunteers from a university. Results indicated significant relationships between codependency and: object relations and reality testing (p = .01), intensity of depression (p < .01), introjective depression (p < .001), and history of abuse (p < .001). The results are supportive of codependency as a useful construct which involves a cluster of difficulties in interpersonal relationships, reality testing, and introjective depression. An association was demonstrated between codependency and parental alcoholism, or history of childhood abuse, or both.

Adult↗