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Biomedical subjects

R Hamilton

Publications and source records attributed to R Hamilton.

At least 55 records · Page 3Linked to original sources
PubMed1984

Heart rate response to tilting in newborns in quiet and active sleep.

The heart rate response to tilting was investigated in active and quiet sleep in 19 normal newborns (age 1-7 days) and 11 healthy premature infants (age 2-19 days). RR intervals were determined by computer from the ECG for 30-60 s periods immediately before and after each tilt. Term infants had a significant (p less than 0.005) decrease in RR interval for head-up tilting and significant (p less than 0.005) increase in RR with head down tilts. There was no significant difference in the magnitude of RR change between upward and downward tilt or between active and quiet sleep. For premature infants, the response to tilting was similar to that of the term infants, especially with allowance for the faster heart rates of the former. Respiratory rate changes were an important source of variability in the heart rate response to tilting and are likely the source of previous inconsistencies. Our results indicate that healthy newborns have a well-developed heart rate response to tilting, suggesting considerable maturity of neural control of heart rate.

Electrocardiography↗
PubMed1983

Phenotypic characteristics of cells derived from precursors of human melanoma.

Of 66 specimens from benign melanocytic nevi, including common acquired and congenital nevi, Spitz tumors (epithelioid cell nevi), and melanocytic nevi with dysplasia, 57 could be grown in tissue culture. The cultured cells were identified as melanocytes by the presence of premelanosomes and melanosomes. Cells from 28 of 32 nevus cultures grew in an anchorage-independent way in soft agar with a colony-forming efficiency between 0.001 and 1%. Clones derived from single cells and soft agar-selected colonies showed marked phenotypic heterogeneity, but all had a limited life span and did not undergo transformation in culture. These cells were nontumorigenic in nude mice. Cultured nevus cells expressed antigens present on melanoma but absent on normal fibroblasts and/or melanocytes as tested with monoclonal anti-melanoma antibodies. The anti-melanoma antibodies bound equally well to dysplastic, congenital, and common acquired nevi. Antigens are released by nevus cells similar to melanoma cells.

Antigens, Neoplasm↗
PubMed1983

Characterization of dog peripheral lymph lipoproteins: the presence of a disc-shaped "nascent" high density lipoprotein.

The distribution, chemical, and apoprotein composition of plasma and peripheral lymph lipoproteins were compared in control and cholesterol-fed dogs. In both groups of animals, the agarose electrophoretic patterns of plasma and lymph lipoproteins were similar. In hypercholesterolemic dogs, beta-very low density lipoprotein, beta-migrating intermediate density lipoprotein, and HDLc were major components both in plasma and lymph, providing evidence for a potential interaction of these atherogenic particles with macrophages and other peripheral cells. The chemical composition and physical appearance of peripheral lymph HDL was markedly different from that of plasma HDL (high density lipoprotein), especially in the cholesterol-fed animals. Lymph HDL had a higher cholesterol to protein ratio and a markedly increased free cholesterol content (free cholesterol to cholesteryl ester ratio of 1.7 as opposed to 0.2 in plasma HDL in cholesterol-fed animals). The phospholipid content of lymph HDL was higher than that of plasma HDL, while the protein content was lower. A significant proportion of lymph HDL obtained from cholesterol-fed dogs was in the form of disc-shaped particles stacked in rouleau structures. Changes in plasma apolipoprotein concentrations due to cholesterol feeding were reflected in peripheral lymph to different degrees, depending largely on the relative size of the lipoproteins containing the individual lipoproteins. A considerable enrichment of lymph HDL with apoE and apoA-IV was observed by both immunochemical and electrophoretic methods. In lymph HDL from control and cholesterol-fed dogs, the apoE/apoA-I and apoA-IV/apoA-I ratios were several-fold elevated, compared to those of plasma HDL. It is concluded, therefore, that during cholesterol feeding a substantial portion of interstitial HDL is assembled de novo in the periphery as a crucial stage of reverse cholesterol transport to the liver. It is likely that further modification occurs upon entry to plasma and exposure to lecithin:cholesterol acyltransferase, possibly leading to generation of HDLc. Alternatively, these particles may be directly and rapidly removed by the liver.

Animals↗
PubMed1982

Melanoma of the male urethra: surgical approach and pathological analysis.

Primary urethral melanoma in male subjects is rare and optimum therapy has not been established. We described a male patient with a primary urethral melanoma that arose in a precursor nevus and was treated by excision, bilateral groin dissections and postoperative radiation therapy. Urinary and sexual functions have been maintained. We review the previously reported cases of urethral melanoma in male subjects. The biologic relationship of melanoma to precursor lesions in mucosal sites is discussed.

Adult↗
PubMed1982

Adjuvant antiplatelet therapy with aspirin in colo-rectal cancer.

Sixty-six patients with Duke's B2 or C colon or rectal cancer were randomized for treatment with aspirin (ASA), 600 mg, p.o., twice daily x 2 years or placebo (P). Compliance was checked in both groups by random measurement of blood salicylate levels. Fifty-seven patients are currently evaluable. No difference in disease-free (p = .66) or overall survival (p = .90) is present between ASA and P groups. The time at which ASA therapy is started (within 2 or within 4 weeks) following surgery does not affect these results. Aspirin at conventional dosage is ineffective in preventing the appearance of metastases in patients with colo-rectal cancer.

Actuarial Analysis↗
PubMed1981

Repeated histamine inhalation tests in asthmatic patients.

Histamine inhalation tests were performed in 12 asthmatic patients using a 2-min tidal breathing inhalation technique. The tests were repeated on separate days with 30-, 60-, and 120-min intervals between inhalation tests. On another day the inhalation tests were repeated four times with 40-min intervals between tests. The geometric mean provocative concentrations of histamine needed to cause a 20% fall in forced expiratory volume in 1 sec (PC20) for the group on the latter study day were 1.67, 1.57, and 1.55 mg/ml (p greater than 0.25) indicating no change in sensitivity to inhaled histamine with repeated testing. The results suggest that cumulative dose-response curves for drugs potentially affecting the airways or antagonizing histamine can be constructed within 1 day using histamine inhalation tests. The data also suggested that an individual PC20 result may be sensitively assessed by comparing it to a +/- 2 SD range from the mean of a series of control or placebo PC20 values.

Adult↗
PubMed1980

The use of microvascular free skin-muscle flaps in management of avulsion injuries of the lower leg.

The authors used microvascular free skin-muscle flaps to cover avulsion wounds in the lower leg of ten patients. There were three children and seven adults, ranging in age from 5 to 54 years. Vessels supplying gracilis (four) and tensor fascia lata (six) skin-muscle units were anastomosed to the anterior tibial (nine) and posterior tibial (one) vessels. The tensor fascia lata unit has a more constant anatomy and is preferred. Principles of management include: 1) early adequate, but conservative, debridement; 2) continuous bony stabilization; 3) preoperative arteriography; 4) anticoagulation; 5) recipient vessel identification in healthy uninjured tissue; 6) appropriate timing; 7) delayed bone grafting.

Adolescent↗
PubMed1980

Microvascular osteocutaneous groin flap in the treatment of an ununited tibial fracture with chronic osteitis. A case report.

A 37-year-old man with an ununited tibial fracture combined with a significant skin defect underwent a microvascular transfer of an island osteocutaneous flap of groin skin and iliac crest bone. The bone component of the flap was shown to be a living transplant by the observation of brisk cancellous bone bleeding when the flap was isolated on its vascular stalk; by rapid fracture healing (weight-bearing 15 weeks postoperatively); and sequential bone scan investigations. Various aspects of the flap blood supply, particularly to bone, are discussed, and reference is made to the use of a more suitable vessel system.

Adult↗
PubMed1980

Specific immunoreactivity of hybridoma-secreted monoclonal anti-melanoma antibodies to cultured cells and freshly derived human cells.

The specificities of monoclonal antibodies against melanoma cells were analyzed using radioimmunoassay, mixed-hemadsorption assay, and quantitative absorption on a variety of malignant and nonmalignant cells. Three of the six hybridoma-secreted antibodies bound to the majority of melanoma cell lines, melanoma tumors, and astrocytoma cell lines as well as to all normal and Epstein-Barr virus-transformed lymphocytes tested. The binding pattern coincides with the presence or absence of the DR antigen on human cells. Conversely, two other antibodies, 19-19 and Nu4B, detected two different antigens common to melanoma and astrocytoma cells only. Cloning of melanoma cells resulted in establishment of DR-positive and DR-negative clones, with the binding of Nu4B antibody retained in all.

Animals↗
PubMed1979

Construction and cloning of rat albumin structural gene sequences.

A recombinant plasmid containing a DNA segment complementary to rat liver albumin mRNA has been constructed, cloned, and used to examine the organization of albumin gene. The 18S fraction of total liver poly(A)-containing RNA was copied into a double-stranded cDNA by avian myeloblastosis virus reverse transcriptase and Escherichia coli DNA polymerase I. The cDNA was inserted into the HindIII site of the plasmid pBR322 via the addition of specific oligonucleotide linkers. Recombinant plasmids were screened by hybrid arrest of mRNA translation and hybridization with specific cDNAs. Thereby, a plasmid was identified that contained a 1200-nucleotide insert corresponding to a segment adjacent to the 5'-terminal region of albumin mRNA. The inserted sequence was used as a hybridization probe to detect five EcoRI fragments of genomic DNA which encode albumin mRNA. These were compared to eight EcoRI fragments identified within the rat genome by albumin cDNA. We conclude that the albumin gene (or genes) is interrupted at more than one site in the coding DNA by intervening sequences. Furthermore, we were able to distinguish those fragments that encode the 5' and 3' ends of the mRNA.

Animals↗