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Biomedical subjects

J H Hill

Publications and source records attributed to J H Hill.

At least 19 recordsLinked to original sources
PubMed1992

Complete nucleotide sequences of two soybean mosaic virus strains differentiated by response of soybean containing the Rsv resistance gene.

The complete nucleotide sequence of the genomic RNAs of strains G2 and G7 of soybean mosaic virus were determined. In both cases, the genome is 9588 nucleotides long, excluding the 3'-terminal poly(A) sequence. A large open reading frame (nucleotides 132 to 9329) encodes a polyprotein of 3066 amino acids with a predicted M(r) of either 349542 (strain G2) or 349741 (strain G7). Based on comparison with the proposed locations of cleavage sites of other potyvirus polyproteins, nine mature proteins are predicted. The mature proteins of the two strains share 94 to 100% amino acid identity, with the greatest variability occurring in the 35K and 42K proteins. Differences in local net charge in portions of these proteins as well as differences in amino acid sequence throughout the genome are discussed in relation to resistance and susceptibility of host plants to strains G2 and G7. Comparison with other potyviruses may be useful for taxonomic clarification of viruses and strains.

Amino Acid Sequence↗
PubMed1991

Effect of intracanalicular collagen implants on the absorption of topically applied sodium fluorescein.

Absorbable intracanalicular collagen implants were placed in both canaliculi of one eye of nine human volunteers. The other eye served as a control. Twenty-four hours later 2% sodium fluorescein was placed into both conjunctival sacs. Serial corneal fluorescein concentrations were measured with a scanning ocular fluorophotometer from 2 to 90 min after fluorescein administration. The mean corneal fluorescein concentration averaged over all time points was greater in 7 of 9 eyes with collagen implants compared to unimplanted controls. When the data from each subject were analyzed collectively, the mean corneal fluorescein concentration in the implanted eyes (1,218 micrograms/ml +/- SEM 83) was significantly greater (p less than 0.001) than the mean concentration in the control eyes (823 micrograms/ml +/- SEM 83). The use of absorbable intracanalicular collagen implants may increase the bioavailability of topically applied ocular solutions.

Absorption↗
PubMed1991

Nucleotide sequences of the coat protein genes of two aphid-transmissible strains of soybean mosaic virus.

The nucleotide sequences of the coat protein genes and 3' non-coding regions of two aphid-transmissible isolates (G2 and G7) of soybean mosaic virus (SMV) were determined. The coat protein of the G2 isolate differs from that of the aphid non-transmissible N isolate by a single amino acid at position 12 (aspartic acid in N, glycine in G2 and G7). The G7 isolate differs from G2 and N at three and four amino acid residues, respectively. The nucleotide sequence similarity of the three isolates in the coat protein coding and 3' non-coding regions ranges from 93 to 100%, respectively. In contrast, watermelon mosaic virus 2 (WMV 2) is only 77% to 79% similar to the SMV isolates, suggesting that WMV 2 is a distinct virus and not an isolate of SMV as proposed previously.

Amino Acid Sequence↗
PubMed1991

A community's response to childhood drownings. A model for accident prevention.

The prevention of drowning or any other accidental injury depends primarily on changing the behavior patterns of the families of the children at risk. Many community organizations and individual citizens must be recruited to help convince the public of the risks of young children drowning in backyard pools and to propose appropriate prevention measures. Legally mandated remedies may be necessary and may take years to show any significant effect. Because of the constantly changing population of parents of young children and the high risk of drowning for small children in Arizona, the educational programs must be repeated year after year.

Arizona↗
PubMed1990

Genetic engineering of plants for virus resistance.

Historically, control of plant virus disease has involved numerous strategies which have often been combined to provide effective durable resistance in the field. In recent years, the dramatic advances obtained in plant molecular virology have enhanced our understanding of viral genome organizations and gene functions. Moreover, genetic engineering of plants for virus resistance has recently provided promising additional strategies for control of virus disease. At present, the most promising of these has been the expression of coat-protein coding sequences in plants transformed with a coat protein gene. Other potential methods include the expression of anti-sense viral transcripts in transgenic plants, the application of artificial anti-sense mediated gene regulation to viral systems, and the expression of viral satellite RNAs, RNAs with endoribonuclease activity, antiviral antibody genes, or human interferon genes in plants.

Base Sequence↗
PubMed1988

Panendoscopy in screening for synchronous primary malignancies.

The entire upper aerodigestive tract must be evaluated at the time of initial tumor evaluation in patients with squamous cell carcinoma of the head and neck. The necessity of panendoscopy (laryngoscopy, bronchoscopy, esophagoscopy) in this evaluation has not been demonstrated convincingly. Between January 1, 1984 and December 31, 1985, 208 patients with previously untreated squamous cell carcinoma of the head and neck were analyzed prospectively. These patients underwent head and neck examination, chest radiograph, barium esophagram, and panendoscopy. Fifteen (7.2%) had synchronous malignancies of the upper aerodigestive tract. In four patients (1.9%) the synchronous primary tumor was found only by endoscopy. Three patients (1.4%) had cancers of the hypopharynx. One patient (0.5%) had a bronchial cancer detected only on bronchoscopy. No tumors were detected by esophagoscopy that were not also seen on barium esophagram. We conclude that endoscopic examination of the hypopharynx is very helpful in screening for additional tumors in head and neck cancer patients, but routine esophagoscopy cannot be supported. Screening bronchoscopy cannot be strongly supported due to its very low yield.

Bronchoscopy↗
PubMed1987

Primary culture of squamous head and neck cancer with and without 3T3 fibroblasts and effect of clinical tumor characteristics on growth in vitro.

Twenty-one tumors from patients with squamous cell carcinoma of the head and neck (SCC H/N) were cultured with and without 3T3 fibroblasts in order to determine whether, on the basis of improved tissue culture medium, 3T3 cells could be deleted without altering growth and cloning efficiency. Thirty-five additional primary SCC H/N specimens, cultured in the presence of 3T3 fibroblasts, were studied to assess the effect of tumor differentiation, site of primary tumor, and site of specimen procurement on growth. The authors conclude that 3T3 cells remain essential for optimal growth and cloning efficiency. Also, 3T3 cells improved the number of successful cultures by 33% to 100% depending on the plating density, and cloning efficiency was improved by 50% in the presence of 3T3 cells. Growth did not correlate with tumor differentiation or site of origin of the tumor specimen. Culture of specimens from the primary site resulted in growth significantly more frequently than culture of specimens obtained from metastatic neck nodes.

Carcinoma, Squamous Cell↗
PubMed1986

Porphyrin fluorescence and photosensitization in head and neck cancer.

Indistinct margin demarcation and autofluorescence are problems in fluorescence delineation of porphyrin-containing head and neck squamous cell cancer (HNSCC). We studied the time course and in vivo localization of porphyrin fluorescence in a squamous cell cancer hamster model and in human HNSCC. After intravenous injection, a gradient in fluorescence intensity developed rapidly until tumors fluoresced above a lower-intensity mucosal background. Hamster tumor and ulcerated HNSCC without porphyrin injection demonstrated autofluorescence grossly indistinguishable from fluorescence in porphyrin-injected tumors. However, fluorescence microscopy revealed autofluorescence to be a surface phenomenon and showed injected porphyrin localized in tumor stroma. We conclude that autofluorescence must be considered when interpreting porphyrin fluorescence. In addition, empirically designed photodynamic therapy can be effective in selected HNSCC. Data from animal experiments provide useful guidelines for the delivery of this therapy.

Aged↗
PubMed1986

Fluorescent microscopy of hematoporphyrin derivative in the nude mouse tumor model.

Mechanisms for localization of hematoporphyrin derivative (HPD) within malignant tissue and for tumor necrosis after photodynamic therapy have not yet been established with certainty. We describe a modified freeze-drying technique to study these mechanisms. Normal tissues and squamous cell carcinoma xenografts were examined in nude mice after administration of HPD. Skin reveals marked fluorescence in connective tissue cells. No fluorescence is visible in surface epithelial cells or keratin. Liver shows diffuse fluorescence only in cells lining sinusoids. In tumor, malignant cells do not fluoresce and connective tissue cells fluoresce brilliantly. This technique provides a clear view of HPD fluorescence, frozen instantaneously in location and time. Fluorescence from connective tissue cells in skin and tumor suggests that localization and photodynamic action may be targeted in part at cells that critically support malignant epithelial cell growth as well as at malignant epithelial cells directly.

Animals↗
PubMed1986

Photodynamic therapy for head and neck cancer xenografts in athymic mice.

This study examines efficacy and optimal treatment variables of photodynamic therapy (PDT) for human head and neck squamous cancer (HNSC) xenografts in athymic mice. Two and four days after injection of hematoporphyrin derivative (HPD), tumors were illuminated with red light from an argon-dye laser. Sixty-three tumors were treated. With HPD dose and light intensity constant at 7.5 mg/kg and 100 mW/cm2, respectively, the extent of tumor necrosis was strongly dependent on duration of light exposure. There was no substantial difference in results for 30- and 60-minute treatment durations between animals injected with HPD 2 and 4 days before treatment. After 30 minutes treatment time, responses were seen in 8 of 10 mice (2 days post-HPD) and 11 of 12 mice (4 days post-HPD). After 60 minutes treatment time, toxicity was high. We conclude that, in this model, PDT is effective in selective killing of HNSC. For future comparison studies in this model, if the indicated HPD dose and light intensity are used we recommend a 2-day delay after HPD injection and a light exposure duration of 30 minutes.

Animals↗
PubMed1986

Primary mandibular reconstruction using the AO reconstruction plate.

Primary reconstruction of segmental defects of the mandible following cancer resection remains a major problem. In 1976, a stainless steel plate was developed by AO/ASIF (Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation) for mandibular reconstruction. This plate completely stabilizes both mandibular stumps without the need for intermaxillary or external fixation. In addition, when bone grafting is performed, the design of this plate promotes revascularization by allowing maximal contact between grafted cancellous bone and surrounding soft tissue. Since April 1985, we have used this reconstruction plate in six patients undergoing composite resection. The technique did not compromise cancer resection, excessively prolong operating time, or alter postoperative management. All six patients have retained the AO reconstruction plate and have been reconstructed successfully with achievement of satisfactory function and cosmesis.

Adult↗
PubMed1986

Light dosimetry in animal models: application to photodynamic therapy in otolaryngology.

Photodynamic therapy (PDT) for treatment of head and neck cancer uses a photoactive compound that is illuminated with 630 nm (red) light. The effectiveness of PDT depends on the penetration of light into tissue that is both tissue and wavelength dependent. The characterization of the optical properties of an animal oral mucosa and skin has been done to determine the amount of light below these tissues available to be used for photodynamic therapy. The tissue absorbance of visible light from 400 nm to 700 nm has been determined in vitro for hamster check pouch mucosa and for athymic mouse skin. The pattern of absorbance is similar for both tissues and demonstrates greater transmission at the longer wavelengths. The diffuse transmittance of light in vivo for these animal models was measured with an interstitial fiberoptic probe. At 630 nm the diffuse transmittance for nude mouse skin averages 10% of the incident light energy, and that for the hamster mucosa almost 50% of the incident light energy.

Animals↗