Field studies on seed germination and seedling development in Zostera marina L.

Seeds of Zostera marina L. were collected in July 1978 and July 1979 and planted within two weeks in sediment-filled containers in shallow water at Northwest Creek, New York. The containers were retrieved at periodic intervals over the next 12 months and the seeds and seedlings examined. Between 76 and 93% of the recovered seeds germinated; primarily during October–December, 3–4 months after release. Seedling growth and development occurred during the autumn and spring, but not in winter. A progressive loss of seedlings was observed during the winter and spring, however, and none survived past May.Three stages of seedling development were distinguished. Stage 1 represented germination including emergence and straightening of the cotyledon. Stage 2 seedlings exhibited continued growth of the cotyledon and variable, but often extensive, elongation (2–50 mm) of the axial hypocotyl. The plumule remained undeveloped (length ? 3 mm), and there were no hairs on the basal hypocotyl. Stage 3 seedlings showed the same range in axial hypocotyl length, but they were distinguished by the onset of plumule growth and hypocotyl hair formation.     

The Niobrara River Valley,a postglacial migration corridor and refugium of forest plants and animals in the grasslands of central North America

The Niobrara River Valley of northern Nebraska contains numerous bryophyte, vascular plant, and animal species more typical of forests far to the east, north, and west than to other forests in the grasslands that surround the Valley. Some species are probably relicts of cooler glacial and early postglacial times, when much of what is now grassland was covered by boreal and cool-temperate forests. Others entered the Valley from the east in postglacial times, and some entered from the west as the climate became semi-arid. There is a steep decline in total number of vascular plant species from the mouth of the Missouri River up through the Niobrara Valley, suggesting an environmental gradient and differential migration and extirpation of species at various times since the Pleistocene.     

Properties of Statistical Tests of Neutrality for DNA Polymorphism Data

A class of statistical tests based on molecular polymorphism data is studied to determine size and power properties. The class includes TAJIMA''s D statistic as well as the D* and F* tests proposed by FU and LI. A new method of constructing critical values for these tests is described. Simulations indicate that TAJIMA''s test is generally most powerful against the alternative hypotheses of selective sweep, population bottleneck, and population subdivision, among tests within this class. However, even TAJIMA''s test can detect a selective sweep or bottleneck only if it has occurred within a specific interval of time in the recent past or population subdivision only when it has persisted for a very long time. For greatest power against the particular alternatives studied here, it is better to sequence more alleles than more sites.     

An observation of fine tubules within the endoplasmic reticulum in a dog liver

Summary During a survey of liver tissue from 100 dogs, fine tubules were observed within the cisternae of the endoplasmic reticulum of hepatocytes in one dog. The tubules were 300 Å in diameter with electron dense walls of 100 Å thickness. Many cells contained the tubules but their significance is unknown. The tubules varied from other reported microtubules in their location, size and characteristics of fixation and staining.     

Effects of chorda tympani nerve anesthesia on taste responses in the NST

Human clinical and psychophysical observations suggest that the taste system is able to compensate for losses in peripheral nerve input, since patients do not commonly report decrements in whole mouth taste following chorda tympani nerve damage or anesthesia. Indeed, neurophysiological data from the rat nucleus of the solitary tract (NST) suggests that a release of inhibition (disinhibition) may occur centrally following chorda tympani nerve anesthesia. Our purpose was to study this possibility further. We recorded from 59 multi- and single- unit taste-responsive sites in the rat NST before, during and after recovery from chorda tympani nerve anesthesia. During anesthesia, average anterior tongue responses were eliminated but no compensatory increases in palatal or posterior tongue responses were observed. However, six individual sites displayed increased taste responsiveness during anesthesia. The average increase was 32.9%. Therefore, disinhibition of taste responses was observed, but infrequently and to a small degree in the NST At a subset of sites, chorda tympani-mediated responses decreased while greater superficial petrosal-mediated responses remained the same during anesthesia. Since this effect was accompanied by a decrease in spontaneous activity, we propose that taste compensation may result in part by a change in signal-to-noise ratio at a subset of sites.      

Effects of Buprenorphine,Chlorhexidine, and Low-level Laser Therapy on Wound Healing in Mice

Systemic buprenorphine and topical antiseptics such as chlorhexidine are frequently used in research animals to aid in pain control and to reduce infection, respectively. These therapeutics are controversial, especially when used in wound healing studies, due to conflicting data suggesting that they delay wound healing. Low-level laser therapy (LLLT) has been used to aid in wound healing without exerting the systemic effects of therapies such as buprenorphine. We conducted 2 studies to investigate the effects of these common treatment modalities on the rate of wound healing in mice. The first study used models of punch biopsy and dermal abrasion to assess whether buprenorphine HCl or 0.12% chlorhexidine delayed wound healing. The second study investigated the effects of sustained-released buprenorphine, 0.05% chlorhexidine, and LLLT on excisional wound healing. The rate of wound healing was assessed by obtaining photographs on days 0, 2, 4, 7, and 9 for the punch biopsy model in study 1, days 0, 1, 2, 4, 6, 8, 11, and 13 for the dermal abrasion model in study 1, and days 0, 3, 6, and 10 for the mice in study 2. Image J software was used to analyze the photographed wounds to determine the wound area. When comparing the wound area on the above days to the original wound area, no significant differences in healing were observed for any of the treatment groups at any time period for either study. Given the results of these studies, we believe that systemic buprenorphine, topical chlorhexidine, and LLLT can be used without impairing or delaying wound healing in mice.

A recent retrospective analysis using a medical insurance dataset estimated that approximately 8.2 million people experienced wounds ranging from acute to chronic conditions within the particular year analyzed, and estimated that the cost of acute and chronic wound treatments ranged from $28.1 to $96.8 billion dollars.⁵² The projected rise in the number of people experiencing wounds and the cost of wound care products⁵² have made wound healing a growing area of interest in both clinical medicine and research. Wound healing is a complex process that involves many overlapping, intricate physiologic processes. Each step can have associated deviations that may lead to enhanced, altered, impaired, or delayed healing. Animal research has been used to develop a better understanding of the basic, physiologic mechanisms of wound healing. Mice are the most commonly used animal in biomedical research, and they are used to model a host of conditions, including wound healing. Despite known anatomic and physiologic differences between murine and human skin,^17,53 this species is commonly used due to their small size, ease of handling, and relatively low cost. In addition, the overlapping phases of the wound healing process are similar in mice and humans, making mice a valuable model.⁶⁵Pain is inherent to the development of wound models. Pain receptors in the skin are sensitized during the actual wounding process and during the inflammatory response that occurs immediately after wounding.¹⁹ Pain can also occur during the cleansing and treatment of wounds.¹⁹ Just as managing wound pain is critical in human patients, The Guide for the Care and Use of Laboratory Animals (the Guide)³⁰ and other federal guidelines and regulations governing the care and use of laboratory animals strongly encourages the use of analgesics for animals that experience pain and/or distress.³⁰ Pain, which can also cause stress, may evoke a persistent catabolic state and may ultimately delay wound healing.^19,28,31,43 Therefore, adequate pain control is necessary to avoid negatively affecting or altering the wound healing process.As in human medicine, opioids are commonly used to provide analgesia to research rodents. Buprenorphine, a mixed agonist-antagonist opioid,^26,54 is a common analgesic that acts as a very weak partial agonist of the mu opioid receptor and an antagonist of the κ opioid receptor.²⁶ Buprenorphine is frequently used in animals as both a pre- and post-operative analgesic. It works by binding to the opioid receptors in the skin and other tissues. This ligand-receptor binding regulates the physiologic responses of nociception and inflammation,⁷ which are key factors in the process of healing and regeneration. Buprenorphine is often used instead of full mu-opioid receptor agonist drugs, such as morphine or hydromorphone, because it has fewer systemic side effects.²⁸ Despite their common use as analgesics, reports are mixed in terms of whether opioids, as a class, delay or impair wound healing.^11,28,35,40In addition to controlling pain, minimizing wound contamination and preventing infection is critical to wound healing. The use of antiseptics is often favored over the use of antibiotics as the former presents less chance for developing antibiotic resistance.⁶ As an antiseptic, chlorhexidine is commonly used to irrigate, cleanse, and treat cutaneous wounds. Chlorhexidine has high antimicrobial activity against gram-positive and gram-negative bacteria and some fungi and viruses.⁴ Although considered to be relatively safe, reports are conflicting with regard to whether chlorhexidine delays or impairs wound healing.^4,9,50,57Laser techniques have been used medically for many years, and their powerful, but precise capabilities have rendered them a unique surgical and therapeutic modality. In brief, when the electrons of atoms move to higher energy levels, these electrons absorb energy. This excited energy state is unstable and temporary. The natural return of electrons to their more stable ground state releases energy in the form of photons or light. Light Amplification by Stimulated Emission of Radiation (LASERS) are characterized by the photon stimulation of an already excited electron. This stimulation causes the emitted light to be amplified, as demonstrated by the intense, bright light that is emitted from lasers.⁶³ The concept of low-level laser therapy (LLLT) has garnered interest as a therapeutic modality in both human and veterinary medicine. Specifically characterized as laser therapy using a low power output and a low power range, LLLT is distinguished from other forms of laser therapies by certain parameters such as wavelength, pulse rate and duration, total irradiation time, and dose.⁴⁴ Although the mechanism of action for LLLT is not completely understood,^46,64 the absorption of red and near infrared light energy may reduce detrimental, inflammatory substances^13,15,24,56 while simultaneously stimulating restorative processes.^15,24,46,64 The reduced photothermal impact of LLLT⁴⁴ is reported to produce beneficial physiologic and biologic effects including analgesia, reduction in inflammation, and acceleration of healing.⁴⁸ The initial report of LLLT as a therapeutic modality found accelerated wound healing and fur regrowth in mice exposed to LLLT.^13,44,46,64 LLLT has since been used as a sole or adjunct therapy for a variety of conditions including tooth root resorption,⁵⁵ traumatic brain injuries,⁵⁸ and tendon, muscle, and bone injuries.^2,3,25,38Studies conducted to assess the effects of LLLT on healing often use parameters of normal wound healing to analyze how LLLT influences those parameters in comparison to healthy, undamaged tissue and damaged tissue not receiving laser therapy. Despite the numerous studies designed to investigate the effects of LLLT on wound healing, conflicting reports exist regarding its efficacy.^{15,17,46,22,23,24,29,34,38,39,55,56,60,64} A recent study in dogs reported accelerated healing and improved cosmetic appearance of a hemilaminectomy surgical site after LLLT,⁶⁰ while other canine studies reported no significant differences in the healing of surgically induced skin wounds between dogs that did and did not receive LLLT.^22,34 Similarly, in an attempt to study the effects of LLLT in pigs, an animal with skin very similar to that of humans, no significant differences were reported in the healing of surgically created skin wounds between swine that did and did not receive LLLT.²⁹ Studies using diabetic rats with excisional cutaneous wounds reported accelerated wound healing,^17,46 and beneficial results were reported in a similar study using diabetic mice.^56,64 While fewer studies have been conducted on the use of LLLT in rodents without concomitant comorbidities, LLLT has been reported to accelerate wound healing in healthy rodents.^15,24 Conversely, some studies found that LLLT does not accelerate or significantly improve wound healing in rodents.^24,39We performed 2 separate studies to investigate the effects of a commonly used opioid, a topical antiseptic solution, and LLLT on excisional wound healing in mice. At the time the initial study (study 1) was conducted, some of our investigators were reluctant to use the recommended analgesic, buprenorphine, due to concern about interference with their study outcomes. Therefore, we conducted study 1 to determine if a single dose of peri-operative buprenorphine would delay healing of a full-thickness excisional wound or a partial-thickness felt wheel dermal abrasion. We also examined the effects of topical chlorhexidine solution on wound healing. The chlorhexidine concentrations used in study 1 were prepared using our standard operating procedure at that time. Study 2 was conducted after study 1, with the design expanded to evaluate a sustained release buprenorphine formulation and LLLT. Study 2 used a full-thickness excisional biopsy to determine the effect of LLLT on excisional wound healing. Commonly used doses of systemic Buprenorphine Sustained Release (SR) and topical chlorhexidine were also included to evaluate their effect on excisional wound healing. The concentration of chlorhexidine in the revised, approved standard operating procedure had been decreased due to literature suggesting that higher concentrations may inhibit healing.^4,49,61 For both studies, we hypothesized that the use of buprenorphine and chlorhexidine would have no effect on the rate of wound healing, and that LLLT would accelerate wound healing in a full-thickness excision as compared with a control.