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Biomedical subjects

P C Baker

Publications and source records attributed to P C Baker.

At least 19 recordsLinked to original sources
PubMed2005

Diethylene glycol monobutyl ether (DGBE): two- and thirteen-week oral toxicity studies in Fischer 344 rats.

Standard toxicologic endpoints, supplemented by additional examinations, were studied for groups of 10 Fischer 344 rats/sex given drinking water formulated to supply 0, 50, 250, or 1000 mg diethylene glycol monobutyl ether (DGBE)/kg/day for 13 weeks. These dose levels were based upon initial investigations using drinking water formulated to supply 0, 1000, 1500 or 2000 mg DGBE/kg/day for two weeks. All rats survived the respective treatment intervals with no adverse treatment-related in-life effects, including no alterations in a functional observational battery. In both studies, rats given > or = 1000 mg/kg/day consumed less water and feed and weighed slightly less than controls. For rats given > or = 1000 mg DGBE/kg/day, the liver and red blood cells (RBC) were the primary target organs although the effects were slight. In the 13-week study, rats given 1000 mg/kg/day had statistically significant increased relative liver weight (7-10%) and hepatic cytochrome P450s (24-39%) and UGT (approximately 16%) levels along with slight, statistically significant, decreases in serum total protein, cholesterol and aspartate aminotransferase. Histopathologically, very slight hepatocyte hypertrophy and increased individual hepatocyte degeneration were found in females only. At 1000 mg/kg/day, the RBC count, hemoglobin (Hgb) and hematocrit (Hct) were minimally, but statistically significantly, decreased (5.1-8.7%) but RBC morphology, RBC indices, reticuloctye count and bone marrow and spleen histopathology were unaffected. Absolute and relative kidney weights statistically significantly increased (6-13%) with an equivocal increase in minor histopathologic changes typical of early spontaneous nephropathy. There were no adverse effects on urinalysis, clinical chemistry, sperm parameters or testis histopathology. At 250 mg/kg/day, there were equivocal decreases (approximately 2-3%) in RBC count, Hgb and Hct that were statistically significant for the RBC count and Hgb, but these changes were within the historical control range. This dose level was considered the no adverse effect level (NOAEL).

Administration, Oral↗
PubMed2001

The addition of ceftriaxone to oral therapy does not improve outcome in febrile children with urinary tract infections.

OBJECTIVE: To determine whether the addition of a single dose of ceftriaxone sodium to a 10-day course of trimethoprim and sulfamethoxazole hastens urine sterilization or resolution of clinical symptoms in febrile children with urinary tract infections. DESIGN: Prospective, single-blind, randomized study. SETTING: Tertiary care children's hospital emergency department. PATIENTS: Febrile children aged 6 months to 12 years with a presumptive urinary tract infection based on history, physical examination, and urinalysis findings. INTERVENTIONS: A history was taken, a physical examination and urinalysis and culture were performed, and a white blood cell count and erythrocyte sedimentation rate were obtained. Children were randomized to receive an intramuscular dose of ceftriaxone then 10 days of trimethoprim-sulfamethoxazole (IM + PO group) or oral trimethoprim-sulfamethoxazole alone (PO group). After receiving study medication, patients were discharged from the hospital to return in 48 hours for a follow-up evaluation and urine culture. Treatment failure was defined as the persistence of a positive culture at 48 hours or the need for hospital admission for intravenous rehydration or antibiotic therapy. RESULTS: Sixty-nine children were enrolled, 34 in the IM + PO group and 35 in the PO group. The 2 groups were similar at the initial visit with respect to age, sex, clinical degrees of illness, white blood cell count, and erythrocyte sedimentation rate (P>.05). At the 48-hour follow-up visit, there were no differences between the 2 treatment groups in resolution of vomiting, fever, general appearance, abdominal tenderness, and hydration state (P>.05). There were 9 treatment failures, 4 in the IM + PO group and 5 in the PO group (P =.93). CONCLUSION: The addition of a single dose of intramuscular ceftriaxone to a 10-day course of oral trimethoprim-sulfamethoxazole for urinary tract infection with fever resulted in no difference at 48 hours in the urine sterilization rate, degree of clinical improvement, or subsequent hospital admission rate.

Administration, Oral↗
PubMed1993

Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study.

Intrastromal Corneal Rings (ICRs) have been demonstrated to flatten human corneas when implanted into peripheral intrastromal corneal channels. To study the flattening effect, ICRs of increasing thickness, 0.26, 0.31, 0.36, 0.41, and 0.46 mm, were placed into oversized (approximately 70% depth) intrastromal channels in 38 eye-bank eyes. Each of 33 eyes received one ICR; the mean change in dioptric data was obtained for four meridians using an intraoperative photokeratoscope. Intrastromal corneal rings of increasing thickness resulted in corneal flattening of 3.8 +/- 1.1, 4.9 +/- 0.6, 5.2 +/- 1.1, 5.3 +/- 1.9, and 7.3 +/- 1.6 diopters, respectively, for keratoscope mire 2. One of each size ICR was placed into one of five additional eye-bank eyes; the degree of flattening measured by laser holographic interferometry was 1.8, 2.9, 5.5, 4.7, and 10.1 diopters, respectively, for the central 6 mm corneal zone. These results indicate that the ICR provides a fairly linear flattening relationship over the range of thicknesses tested. Additionally, laser holographic interferometry wave unit maps of preoperative and postoperative corneas demonstrated that the ICR tends to preserve positive corneal asphericity if present preoperatively.

Anthropometry↗
PubMed1991

The effects of cocaine upon 5-hydroxyindole levels of the maturing mouse brain.

1. Mice at various ages between birth and adulthood were injected with cocaine hydrochloride (30 mg/kg) and then their brains were assayed for 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA). 2. Changes in the levels of both metabolites were in keeping with 5-HT uptake inhibition at all ages.

Aging↗
PubMed1991

The effects of acute and extended monoamine oxidase inhibition upon 5-hydroxyindoles in maturing mouse brain.

1. Mice of four ages between newborn and adult were exposed to the monoamine oxidase inhibitor amiflamine both acutely and in an extended (5 day) regimen. Brains were then assayed at various times following amiflamine for changes in the levels of serotonin (5-HT, 5-hydroxytryptamine) and 5-hydroxyindole acetic acid (5-HIAA). 2. Although both metabolites initially changed as might be expected, with 5-HT elevating and 5-HIAA decreasing, the younger brains recovered their 5-HT levels slower than older brains and eventually young brains had levels of 5-HIAA that were in excess of normal. At some times both metabolites were in excess of normal at younger ages. 3. These results are compared to changes seen with the 5-HT uptake inhibitor citalopram and it is concluded that in young brain 5-HIAA levels lack firm regulatory control and are not passive reflections of 5-HT changes.

Aging↗
PubMed1990

Chronic citalopram action and the maturing mouse brain's indoleamine levels.

1. Mice of various ages between birth and adulthood were injected daily for 12 days with the serotonin specific uptake inhibitor citalopram (LU 10-171). 2. Two hours, 1 day and 3 days following the last injection animals were killed and their brains assayed for 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA). 3. Changes in levels of both metabolites varied by age of the animal, brain region and time after last injection. These patterns differed from previous studies of shorter duration citalopram exposure. 4. The data support the view that 5-HT and 5-HIAA levels are probably not dependently related in immature brain. Indeed 5-HIAA modulation in the immature seems to lack the firm control of the adult and can be modified for extended periods by citalopram action.

Aging↗
PubMed1989

Neuromuscular symptoms in patients with previous poliomyelitis: a New Zealand study.

Eighteen patients with old poliomyelitis were assessed in order to determine the incidence and severity of late complications. Sixty-one percent complained of new weakness, 83% fatigue and 17% muscle pain. After assessment 33% (six patients) were judged to have significant new weakness and muscle fatigue that could not be explained by other causes, and this group may have postpoliomyelitis progressive muscular atrophy or postpolio syndrome. Onset of symptoms was typically about 30 years after the acute illness; new weakness was relatively mild and progression was slow over many years. Clinically and pathologically this disorder is distinct from idiopathic motor neuron disease, and is not life threatening.

Adult↗
PubMed1988

Indoleamine stores in maturing mouse brain reexposed to citalopram following extended uptake inhibition.

1. Mice of various ages between birth and adulthood were injected daily for 5 days with the serotonin specific uptake inhibitor citalopram (LU 10-171). 2 days later they were reinjected with citalopram 2. 2 hr, 1 day and 3 days following the last injection animals were killed and their brains assayed for 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA). 3. Brains were found to still respond to citalopram's acute action despite the fact younger brains had undergone long term alteration of 5-HIAA stores. 4. The possibility that indoleamines are subject to different regulatory mechanisms in young brain is discussed.

Aging↗
PubMed1987

Indoleamine metabolism in maturing mouse brain following extended uptake inhibition with citalopram.

1. At various ages between birth and adulthood mice were exposed to the specific uptake inhibitor citalopram (Lu 10-171) once a day for 5 days. 2. Their brains were assayed for 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) as well as indoleamine turnover at selected times after termination of the drug. 3. Younger brain differed from older brain in both stores and turnover. 4. Younger brain demonstrated the effects of citalopram action as much as 3 weeks later with continued elevation of 5-HIAA stores. 5. The possibility that 5-HIAA is an active agent in serotonergic neurogenesis is discussed.

Animals↗
PubMed1987

The recovery of maturing brain from acute citalopram exposure.

At various ages between birth and adulthood mice were exposed to the specific 5-HT uptake inhibitor citalopram. Their brains were assayed for indoleamine stores and turnover during the period of recovery from the drug's action. Young brain lacks the ability to fine tune its return to normal following citalopram action.

Animals↗
PubMed1986

Effects of prenatal exposure to lithium on indoleamines in maturing mouse brain.

Levels of the intermediates 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) and activities of the enzymes 5-hydroxytryptophan decarboxylase (5-HTPD) and monoamine oxidase (MAO) were measured in 4 different brain regions of maturing mice exposed to LiCl during prenatal and postnatal development. 5-HT and 5-HIAA levels were reduced significantly in all brain regions of 1 day old mice. 5-HIAA was also reduced in hemispheres of 1 week olds. There were some marginally significant elevations and reductions in 5-HTPD and MAO activity at various ages. It is suggested that lithium is reducing 5-HT synthesis and perhaps storage also but that neonates recover quite rapidly from the prenatal exposure.

Animals↗
PubMed1986

Biochemical and functional effects of fenfluramine in maturing mice.

Biochemical and functional effects of a single dose of fenfluramine were studied in maturing mice aged 1 day or 1, 2 or 6 weeks postpartum. 5-HT and 5-HIAA stores in hemispheres and brain stem were significantly reduced at all ages 1 day after the drug injection. In contrast to adult animals which showed continuing reductions in 5-HT and 5-HIAA 4 weeks after the fenfluramine injection, animals at all younger ages returned to normal by 1 week after the injection. Body weight was reduced 2-4 weeks after fenfluramine injection in 1 week old animals; however 2 week animals showed only a small transient reduction during the first week following fenfluramine. No significant effects were found on body temperature or temperature preference. The results are discussed in relation to the effects of various amine depleting agents.

Age Factors↗
PubMed1985

The neuroanatomy of vomiting in man: association of projectile vomiting with a solitary metastasis in the lateral tegmentum of the pons and the middle cerebellar peduncle.

Animal studies have indicated a "vomiting center" situated in the dorsal portion of the lateral reticular formation of the medulla at the level of the dorsal nucleus of the vagus. There is also a chemoreceptor trigger zone in the floor of the fourth ventricle in the area postrema which influences the vomiting center. A 63 year old man with a three year history of metastatic malignant melanoma presented with nausea, projectile vomiting, gait ataxia and diplopia associated with horizontal and vertical nystagmus. CT scan showed a solitary brainstem metastasis without hydrocephalus and he was treated with radiotherapy with resolution of his vomiting after four weeks. At post mortem three months later a metastasis was found in the right middle cerebellar peduncle and lateral tegmentum of the pons; there was no pathological change in the area of the vomiting center or area postrema. It is postulated that this lesion caused projectile vomiting because of involvement of either afferent projections to the vomiting center. The neuroanatomy of vomiting is discussed.

Brain Neoplasms↗