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Biomedical subjects

R S Baker

Publications and source records attributed to R S Baker.

At least 91 records · Page 5Linked to original sources
PubMed1988

A randomized clinical trial of topical gentamicin after tympanostomy tube placement.

Purulent otorrhea is the most common complication of tympanostomy with tube placement. Some authors report an incidence of over 30%. We have evaluated topical gentamicin solution for prophylaxis in a controlled, randomized, prospective clinical trial. Nine patients of the 102 in the study developed otorrhea in the first two postoperative weeks. All nine were in the control group of 46. The 56 patients receiving prophylactic gentamicin had no cases of purulent otorrhea. Several other characteristics of the patients and the procedures were examined as possible risk factors for otorrhea. None were statistically significant, but the younger patients had a higher rate of infection. We recognize the theoretical risk of ototoxicity, but conclude that instillation of topical gentamicin is an effective prophylactic technique for preventing purulent otorrhea after tympanostomy.

Administration, Topical↗
PubMed1988

Sensitivity of HRA/Skh hairless mice to initiation/promotion of skin tumors by chemical treatment.

HRA/Skh hairless mice were investigated for their sensitivity to initiation and promotion by chemicals because of (a) the known sensitivity of these mice to photocarcinogenesis, (b) their low background papilloma incidence (2/3000 mice under 1 year of age) and (c) ease of treatment and identification of tumors, in the absence of hair. Employing a variety of treatments with 7,12-dimethylbenz[a]anthracene (DMBA) as initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as promoter, it was found that the strain was susceptible to both initiation and promotion. Papilloma incidence was at least equivalent to that observed with other sensitive mouse strains. Following initiation with 2.56 micrograms DMBA, papilloma development was promoter-concentration-dependent, resulting in 22.5 papillomas/mouse at 20 weeks in animals administered 5 micrograms TPA. In the absence of DMBA initiation, TPA treatment was weakly carcinogenic in HRA/Skh mice. This treatment induced a dose-dependent increase in papillomas, one of which progressed to a keratoacanthoma-like tumor after 65 weeks. These results show that HRA/Skh mice are highly sensitive, not only to UV carcinogenesis, but also to chemical initiation and promotion of skin papillomas.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Inhalant allergies to fungi: reactions to bakers' yeast (Saccharomyces cerevisiae) and identification of bakers' yeast enolase as an important allergen.

Forty-seven subjects diagnosed as having inhalant allergies to fungi were tested for allergic sensitivity to bakers' yeast. Skin prick tests with yeast extract showed that 35 subjects responded with wheal reactions that were at least 3 mm while 32 subjects were regarded as clearly RAST-positive to bakers' yeast antigens. Skin and RAST testing with purified enolase from bakers' yeast and comparisons with the whole yeast extract showed that the enzyme is a major allergenic component of the extract. This conclusion was supported by results of electroblotting studies. RAST inhibition experiments demonstrated allergenic cross-reactivity between bakers' yeast, bakers' yeast enolase and Candida albicans.

Allergens↗
PubMed1987

Neurologic complications of the epidermal nevus syndrome.

The epidermal nevus syndrome is a neurocutaneous disorder characterized by distinctive skin lesions and often serious somatic and central nervous system (CNS) abnormalities. We observed four cases of this disorder with epidermal nevi and neurologic manifestations, including mental retardation, seizures, ophthalmologic abnormalities, intracranial aneurysm, and porencephalic cyst. A review of 60 reported cases of the epidermal syndrome and our experience suggest that CNS complications are more likely to be associated with epidermal nevi on the head and that the CNS abnormalities are most often ipsilateral to the skin lesion.

Adolescent↗
PubMed1987

Perimetric findings in functional disorders using automated techniques.

Visual fields were assessed by automated static thresholding techniques in 15 consecutive patients with functional visual loss. Although field abnormalities were recorded in all patients, the pattern of abnormality was not distinguishable from organic loss. Furthermore, no form of reliability testing, including numbers of repetitions, false-positives or false-negatives, root mean square (RMS) evaluation, or percentage of fixation losses, was capable of characterizing functional defects. The authors conclude that automated perimetry, as currently practiced, cannot differentiate functional from organic visual field loss.

Adolescent↗
PubMed1987

Allergenic cross-reactivity of egg-white and egg-yolk proteins. An in vitro study.

The radioallergosorbent test (RAST) and RAST inhibition test were used to examine cross-allergenicity amongst the major hen's egg-white and egg-yolk proteins. Using ovalbumin as a reference allergen to compare cross-reactivity, it was apparent that the proteins conalbumin, ovomucoid and lysozyme substantially inhibited binding to ovalbumin discs of IgE in the sera of patients clinically hypersensitive to egg. The converse situation with conalbumin, ovomucoid and lysozyme on the discs and ovalbumin as the inhibitor also resulted in significantly decreased levels of IgE binding to the proteins on the discs. It was also demonstrated that cross-reactions occurred between ovalbumin and the yolk protein, apovitellenin I. Cross-reaction was also observed surprisingly when egg lysozyme was on the disc and the milk protein allergen alpha-lactalbumin was used as the inhibitor. The demonstration of cross-reaction between all of these proteins may signify that there are a number of common allergenic determinants on these egg proteins, thus providing a molecular basis for the phenomenon of cross-reactivity.

Adolescent↗
PubMed1987

Visual loss in cryptococcal meningitis.

Optic neuropathy with visual loss is a well-known complication of chronic elevated intracranial pressure. The association of visual loss with cryptococcal meningitis may reflect the intracranial hypertension often seen in this condition. However, the generally poor results of optic nerve sheath fenestration and analysis of autopsy cases have led to the suggestion that direct invasion of the visual system by organisms may be the more common mechanism of visual loss. We describe a patient with severe visual loss from cryptococcal meningitis in whom organisms were demonstrated in the optic nerve sheath obtained at the time of fenestration. This is the first report to demonstrate this finding in a living patient.

Adult↗
PubMed1987

Magnetic resonance imaging of the posterior fossa in ocular motility disorders--four case studies.

The superiority of magnetic resonance imaging (MRI) of the posterior fossa over x-ray computed tomography is demonstrated by four patients with neuro-ophthalmologic disorders. Advantages of this technique include lack of ionizing radiation, direct multiplanar imaging, increased sensitivity to pathology, increased tissue contrast, and no known adverse effects. It is concluded that MR, when available, should be the imaging modality of choice in patients with neuro-ophthalmologic disorders of suspected brainstem origin.

Adolescent↗
PubMed1987

New muscle growth in denervated extraocular muscle.

Current therapies for paralytic ocular motility disorders often provide less than satisfactory results. Promising new techniques of nerve grafting and muscle transplantation used to treat muscle paralysis elsewhere in the body may have application to the ocular motor system. In studying a procedure designed to reinnervate paretic extraocular muscle (e.o.m.), we produced not only the expected nerve growth but also abundant new muscle growth. A considerable amount of this muscle growth occurred within the axon depleted nerve fascicles of the paretic muscle, suggesting that this structure was a particularly good matrix for muscle fiber growth. These observations suggest that new, entire neuromuscular units may be induced to grow in the plane of a paretic muscle if appropriate surface characteristics can be established.

Animals↗
PubMed1986

Influence of HLA-DR phenotype and myopia on the risk of nonproliferative and proliferative diabetic retinopathy.

The relationship between HLA-DR phenotype, refractive error, and risk of both nonproliferative and proliferative diabetic retinopathy was studied among 227 insulin-dependent diabetics participating in a case-control study of diabetic retinopathy. In the absence of myopia, risk of both proliferative and nonproliferative diabetic retinopathy was increased for HLA-DR phenotypes 4/0, 3/0, and X/X (HLA susceptible) compared to HLA-DR phenotypes 3/4, 3/X, and 4/X (HLA nonsusceptible). Odds ratios equalled 11.8 and 7.4 respectively. In the presence of myopia this increased risk associated with HLA status was abolished. Myopia decreased the risk of proliferative and nonproliferative diabetic retinopathy among HLA-susceptible individuals, odds ratio equalled .09 and .09, but had no protective influence among HLA-nonsusceptible individuals.

Aged↗
PubMed1986

Toxic and genotoxic action of electric-arc welding fumes on cultured mammalian cells.

Welding fumes generated by manual metal arc welding (MMAW) with an automatic welding machine were extracted with water and both the soluble and insoluble fractions were investigated for mitotic delay and for sister chromatid exchange (SCE) induction in cultured Chinese hamster lung (Don) cells. Five flux-coated electrodes of varying composition were chosen as representative of those available. In general, water-soluble and water-insoluble fractions induced SCE in proportion to their chromium(VI) content, and any contribution from chromium(III), fluorides, nickel, manganese or other fume constituents was minor. However, mitotic delay could not be explained in terms of the chromium(VI) concentration alone. This indicated that other components of both the soluble and insoluble fractions of the fumes were capable of inducing mitotic delay. The activity of insoluble fume fractions, either in mitotic delay- or in SCE-induction, was markedly less than that of soluble fractions. This was presumably because of the lower, though still significant, bioavailability of 'insoluble' components of the fume particles.

Air Pollutants, Occupational↗
PubMed1986

Perimetric findings in pseudotumor cerebri using automated techniques.

The authors obtained automated static threshold visual fields in 44 eyes of 22 patients with pseudotumor cerebri. Severe defects were found in 9% and moderate defects in 68%. The pooled incidence of three recent studies using manual kinetic techniques also demonstrated 9% severe defects, but only 34% of eyes demonstrated moderate loss. In 20 of 44 eyes, the papilledema was felt to be severe or atrophic. In none of these eyes was a normal field obtained. Visual field defects in pseudotumor cerebri appear to be more common than previously thought.

Adult↗
PubMed1986

7-Methylbenz[c]acridine: mutagenicity of some of its metabolites and derivatives, and the identification of trans-7-methylbenz[c]-acridine-3,4-dihydrodiol as a microsomal metabolite.

The presence of the proposed proximate carcinogen, trans-3,4-dihydro-3,4-dihydroxy-7-methylbenz[c]acridine (7MBAC-3,4-DHD) among the liver microsomal metabolites of 7-methylbenz[c]acridine (7MBAC) has been demonstrated using gas chromatography mass spectrometry (GCMS) and by co-chromatography with synthetic standards on reverse and normal phase h.p.l.c. 7MBAC-3,4-DHD represented 2.2-3.4% of the total ethyl acetate-extractable metabolites formed from 7MBAC by liver microsomes prepared from untreated and induced rats. About 2.3-2.7% of metabolites formed by lung microsomes was identified as 7MBAC-3,4-DHD. Mutagenicity studies with 7MBAC-3,4-DHD have been carried out in bacterial and mammalian systems using S9 fractions derived from rats pre-treated with Aroclor and guinea pigs pre-treated with 3-methylcholanthrene. Comparative data with other 7MBAC derivatives are also reported. The 7MBAC-3,4-DHD and the analogous dihydro derivative of 7MBAC were the most potent mutagens of those compounds requiring metabolic activation. The data imply that the 3,4-dihydrodiol is metabolised to a bay region diol epoxide as the ultimate carcinogen. In support of this anti-1,2-epoxy-trans-3,4-dihydroxy-7-methyl-1,2,3,4- tetrahydrobenz[c]acridine was a potent mutagen in the Ames and V79 cell systems without activation. The syn-isomer was less active.

Acridines↗
PubMed1986

Urine mutagenicity as an indicator of exposure to dietary mutagens formed during cooking of foods.

Studies were undertaken with individuals fed fried bacon meals to determine whether fruit or vegetables, ingested along with bacon, modified uptake and subsequent excretion of bacon mutagen(s). Urinary mutagenic activity was significant in those who had consumed bacon or mixed bacon/vegetable or bacon/fruit meals within the previous 2 to 3 hr period. Although urine activity varied by a factor of 4 among 15 subjects who consumed different meals, there was no evidence from this investigation that fruit or vegetables contributed to the inherent variability in total urinary mutagenic activity. However, some differences in excretion kinetics may be attributable to vegetable or fruit supplements in mixed meals.

Animals↗
PubMed1985

Multiple factors in the prediction of risk of proliferative diabetic retinopathy.

To identify risk factors for the development of proliferative diabetic retinopathy, we compared 111 patients with longstanding insulin-dependent diabetes who had proliferative retinopathy (cases) with 81 patients with diabetes of similar duration (an average of 26 years) who did not have proliferative diabetic retinopathy (controls). The cases had diabetes that was more difficult to manage, as evidenced by their more frequent blood sugar levels above 200 mg per deciliter (11 mmol per liter) on routine clinic visits (odds ratio, 1.6 for each increment of 10 per cent in the relative frequency), and they expended less effort in managing their diabetes, as indicated by their less frequent testing of urine for sugar (odds ratio, 0.3). Among those who did not have myopia, the cases also had an excess of the HLA-DR phenotypes 4/0, 3/0, or X/X (odds ratio, 10.0). Among those with myopia, these phenotypes did not carry an increased risk of proliferative retinopathy. These results support a multifactorial model for the development of proliferative diabetic retinopathy; however, the mechanisms of action of the identified factors remain unknown.

Adolescent↗
PubMed1985

Visual loss in pseudotumor cerebri of childhood. A follow-up study.

The occurrence of visual loss in substantial numbers of adult patients with pseudotumor cerebri is well recognized. In children, the disease has been said to spare the visual system. We evaluated the ophthalmologic features of 36 children with pseudotumor cerebri followed up for one to 12 years. Four patients had rapid, severe loss of visual acuity and visual field changes while receiving medical therapy. Six others had less-severe but prominent abnormalities of visual acuity and/or visual fields at some point during the disease process. Only one patient had a permanent, severe visual impairment, but five had moderate permanent visual abnormalities. A severe degree of papilledema was seen only in the group with visual loss, but some patients in this group had only moderate papilledema. More patients with dural sinus thrombosis had serious visual loss than did those with other associated diseases or idiopathic pseudotumor cerebri. Quantitative perimetry of some sort can be performed in most children and is the preferred sequential test for planning treatment.

Adolescent↗