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Biomedical subjects

J Marvin

Publications and source records attributed to J Marvin.

At least 19 recordsLinked to original sources
PubMed2001

Mechanics of venom expulsion in Crotalus, with special reference to the role of the fang sheath.

A combination of anatomical and experimental preparations were used to explore the function of the venom delivery system in rattlesnakes (Crotalus). The distal end of the venom duct is compressed near the point where it empties into the venom chamber, a space surrounding the fang defined by the fang sheath. Within the venom chamber, the inner fang membrane lies obliquely over the base of the fang at least partially occluding the entrance orifice. When the fang is retracted the combination of the compressed venom duct and the spatial position of the inner fang membrane serve to inhibit or block venom flow. As the fang is erected beyond approximately 60 degrees (relative to the roof of the mouth) localized compression of the fang sheath decreases the size of the venom chamber, relieves the compressive force from the venom duct, and displaces the inner fang membrane away from the entrance orifice of the fang. Pressure recordings taken at different locations along the venom delivery system demonstrate that the venom gland produces suction during relaxation of the extrinsic glandular musculature. These findings suggest that the venom delivery system of Crotalus is both more flexible and more regulated than previously assumed.

Animals↗
PubMed1999

The mechanics of sound production in the puff adder bitis arietans (Serpentes: viperidae) and the information content of the snake hiss

Puff adders (Bitis arietans), like many other snakes, hiss as part of their defensive repertoire. In B. arietans, the hisses have a clear quadraphasic pattern consisting of an initial exhalatory hiss, a brief transitional pause, an inhalatory hiss and a rest or breath-holding phase. Simultaneous recordings of body diameter, electrical activity in the intrinsic laryngeal musculature, airflow through the nasal passageway and sound production revealed that the anterior respiratory tract plays a passive role in hissing and that the costal pump is responsible for generating the quadraphasic pattern. During hissing, B. arietans uses the same mechanics previously described for normal respiratory ventilation in snakes. Analyses of artificial hisses reveal that the anterior respiratory tract of B. arietans has little ability to modify an exhalant airstream acoustically. The combination of the simple ventilatory mechanics used during hissing and the lack of acoustic modification of the exhalant airstream results in the production of an acoustically simple hiss. Cross-correlation matrix analyses of a variety of snake hisses showed a high degree of acoustic similarity between the sounds, almost approaching the levels determined for white noise. This high level of acoustic similarity reflects the low level of acoustic specialization within the sounds produced by snakes and the low potential for encoded information content.

Journal Article↗
PubMed1992

Hormone levels in vegetarian and nonvegetarian teenage girls: potential implications for breast cancer risk.

Between September 1984 and June 1985, a total of 75 adolescent girls, 35 vegetarians residing in a Seventh-Day Adventist school and 40 nonvegetarians residing in a private non-Adventist boarding school, underwent measurement of their plasma hormone levels in the follicular and luteal phase of their menstrual cycles as well as dietary intake measured by 3-day food records, medical history, height, and weight. There were no significant differences between vegetarians and nonvegetarians in average age of the girls, weight, body mass index, age at menarche, years since the onset of menstruation, or percentage of girls with ovulatory cycles. Vegetarian girls had significantly higher levels of log follicular estradiol [2.00 +/- 0.27 (SD) versus 1.85 +/- 0.27 pg/ml, P less than or equal to 0.05] and luteal dehydroepiandrosterone sulfate (DHS) (1.88 +/- 0.71 versus 1.45 +/- 0.80 microgram/ml, P less than or equal to 0.05) than nonvegetarian girls. Follicular DHS was higher in vegetarians than in nonvegetarians (1.72 +/- 0.79 versus 1.45 +/- 0.95 microgram/ml), but the difference was not significant. The differences in follicular and luteal DHS, but not the difference in log estradiol, were significant (P less than or equal to 0.05) after controlling for ovulation, smoking, and alcohol intake with multivariable regression analysis. There were no significant differences in testosterone or in percentage free estradiol levels between vegetarians and nonvegetarians. Smoking was significantly associated with follicular and luteal DHS and with percentage free follicular estradiol, while alcohol use was significantly and inversely associated with percentage free follicular estradiol after controlling for other variables. The implications for breast cancer risk are discussed.

Adolescent↗
PubMed1986

Meperidine disposition in burn patients.

Limited information is available describing the pharmacokinetics of hepatically-cleared drugs in burn patients. Based on the hypothesis that after burn injury, plasma meperidine clearance should increase in response to the postburn increase in hepatic blood flow, we examined the kinetics of intravenous meperidine in eleven patients about one week after burn injury (acute study) and in five of these patients about six weeks postburn (convalescent study). The meperidine steady-state distribution volume (about 2 1/kg) during both the acute and the convalescent studies was about half the distribution volume reported in the literature for meperidine in healthy subjects. The meperidine clearance in burn patients (acute, 420 ml/min and convalescent, 600 ml/min) was lower than would be anticipated in the presence of known marked increases in hepatic blood flow in burn patients.

Adolescent↗
PubMed1981

Minor burns: guidelines for successful outpatient management.

Minor burns are not necessarily trivial. They often involve dynamic or cosmetically important body areas, and outpatient treatment is not always indicated. Hospitalization is usually necessary for the very young or the elderly; those with deep partial-thickness or full-thickness burns; those with burns of the hand, face, foot, or perineum; those who are alcoholics, demented, or economically deprived; and those who have another illness or injury. Hospitalization is mandatory in cases of suspected child abuse or neglect. Superficial partial-thickness burns can be managed in a variety of ways, including application of biologic dressings and synthetic skin coverings. Most deep partial-thickness burns and all full-thickness ones should be considered for early excision and grafting. All but the most superficial burns require maintenance of joint function and long-term follow-up.

Adult↗
PubMedDate not supplied

Burn depth: a review.

Despite the plethora of technologic advances, the most common technique for diagnosing burn depth remains the clinical assessment of an experienced burn surgeon. It is clear that this assessment is accurate for very deep and very shallow burns. But since clinical judgment is not precise in telling whether a dermal burn will heal in 3 weeks, efforts to develop a burn depth indicator are certainly warranted to accurately determine which dermal burns to excise and graft. This review summarizes the considerable literature in which a variety of techniques to determine burn depth have been used.

Animals↗
PubMedDate not supplied

Anesthesia-assisted procedures in a burn intensive care unit procedure room: benefits and complications.

A retrospective review of 109 procedures was performed to evaluate the safety and efficacy of anesthesiologist-administered anesthesia in the burn intensive care unit treatment room. Intraprocedural and postprocedural complications, impact on patient activity, and nutritional goals were evaluated. The review suggested that these procedures can be performed safely with appropriate supervision and monitoring without detrimental effects on patient activity level or nutritional status.

Adult↗
PubMedDate not supplied

Use of pain assessment tools: is there a preference?

The burn nursing Delphi study identified pain management as the most important area of burn nursing research. The question, "What is the best method to measure the pain of the patient with burns?" ranked in the top 10% of the nursing research priorities and is the research question of this study. The most commonly used pain assessment tools were determined in a 1994 survey of burn centers. Of those that responded, 67% used the Visual Analog Scale and 43% used an adjective scale. Forty patients were enrolled in this prospective, multicenter study. Visual analog and color scales were used during a 3-day cycle and word and faces scales were used during another 3-day cycle. Pain levels were assessed twice each day, once during a quiet time and then again immediately after a painful activity. At the end of each 3-day cycle the patient was asked which tool he or she preferred. At the completion of the study period the patient was asked to select the overall most preferred tool for pain assessment. Although this study indicates that patients prefer the faces and color scales to the most commonly used visual analog and adjective scales, further research is needed to determine the potential impact of preferred tools on pain intervention. The results may also lead burn centers to re-evaluate current selection of pain assessment tools.

Adult↗