Cold nociception as a measure of hyperalgesia during spontaneous heroin withdrawal in mice

Opioids are powerful analgesic drugs that are used clinically to treat pain. However, chronic opioid use causes compensatory neuroadaptations that result in greater pain sensitivity during withdrawal, known as opioid withdrawal-induced hyperalgesia (OWIH). Cold nociception tests are commonly used in humans, but preclinical studies often use mechanical and heat stimuli to measure OWIH. Thus, further characterization of cold nociception stimuli is needed in preclinical models. We assessed three cold nociception tests-thermal gradient ring (5-30 °C, 5-50 °C, 15-40 °C, and 25-50 °C), dynamic cold plate (4 °C to -1 °C at -1 °C/min, -1 °C to 4 °C at +1 °C/min), and stable cold plate (10 °C, 6 °C, and 2 °C)-to measure hyperalgesia in a mouse protocol of heroin dependence. On the thermal gradient ring, mice in the heroin withdrawal group preferred warmer temperatures, and the results depended on the ring's temperature range. On the dynamic cold plate, heroin withdrawal increased the number of nociceptive responses, with a temperature ramp from 4 °C to -1 °C yielding the largest response. On the stable cold plate, heroin withdrawal increased the number of nociceptive responses, and a plate temperature of 2 °C yielded the most significant increase in responses. Among the three tests, the stable cold plate elicited the most robust change in behavior between heroin-dependent and nondependent mice and had the highest throughput. To pharmacologically characterize the stable cold plate test, we used μ-opioid and non-opioid receptor-targeting drugs that have been previously shown to reverse OWIH in mechanical and heat nociception assays. The full μ-opioid receptor agonist methadone and μ-opioid receptor partial agonist buprenorphine decreased OWIH, whereas the preferential μ-opioid receptor antagonist naltrexone increased OWIH. Two N-methyl-d-aspartate receptor antagonists (ketamine, MK-801), a corticotropin-releasing factor 1 receptor antagonist (R121919), a β2-adrenergic receptor antagonist (butoxamine), an α2-adrenergic receptor agonist (lofexidine), and a 5-hydroxytryptamine-3 receptor antagonist (ondansetron) had no effect on OWIH. These data demonstrate that the stable cold plate at 2 °C yields a robust, reliable, and concise measure of OWIH that is sensitive to opioid agonists.

Neuroimmune Activation and Microglia Reactivity in Female Rats Following Alcohol Dependence

The rates of alcohol use disorder among women are growing, yet little is known about how the female brain is affected by alcohol. The neuroimmune system, and specifically microglia, have been implicated in mediating alcohol neurotoxicity, but most preclinical studies have focused on males. Further, few studies have considered changes to the microglial phenotype when examining the effects of ethanol on brain structure and function. Therefore, we quantified microglial reactivity in female rats using a binge model of alcohol dependence, assessed through morphological and phenotypic marker expression, coupled with regional cytokine levels. In a time- and region-dependent manner, alcohol altered the microglial number and morphology, including the soma and process area, and the overall complexity within the corticolimbic regions examined, but no significant increases in the proinflammatory markers MHCII or CD68 were observed. The majority of cytokine and growth factor levels examined were similarly unchanged. However, the expression of the proinflammatory cytokine TNFα was increased, and the anti-inflammatory IL-10, decreased. Thus, female rats showed subtle differences in neuroimmune reactivity compared to past work in males, consistent with reports of enhanced neuroimmune responses in females across the literature. These data suggest that specific neuroimmune reactions in females may impact their susceptibility to alcohol neurotoxicity and other neurodegenerative events with microglial contributions.

Predator-induced transgenerational plasticity of parental care behaviour in male three-spined stickleback fish across two generations

Parental care is a critical determinant of offspring fitness, and parents adjust their care in response to ecological challenges, including predation risk. The experiences of both mothers and fathers can influence phenotypes of future generations (transgenerational plasticity). If it is adaptive for parents to alter parental care in response to predation risk, then we expect F1 and F2 offspring who receive transgenerational cues of predation risk to shift their parental care behaviour if these ancestral cues reliably predict a similarly risky environment as their F0 parents. Here, we used three-spined sticklebacks (Gasterosteus aculeatus) to understand how paternal exposure to predation risk prior to mating alters reproductive traits and parental care behaviour in unexposed F1 sons and F2 grandsons. Sons of predator-exposed fathers took more attempts to mate than sons of control fathers. F1 sons and F2 grandsons with two (maternal and paternal) predator-exposed grandfathers shifted their paternal care (fanning) behaviour in strikingly similar ways: they fanned less initially, but fanned more near egg hatching. This shift in fanning behaviour matches shifts observed in response to direct exposure to predation risk, suggesting a highly conserved response to pre-fertilization predator exposure that persists from the F0 to the F1 and F2 generations.

The neuroimmune system - Where aging and excess alcohol intersect

As the percentage of the global population over age 65 grows, and with it a subpopulation of individuals with alcohol use disorder (AUD), understanding the effect of alcohol on the aged brain is of utmost importance. Neuroinflammation is implicated in both natural aging as well as alcohol use, and its role in alterations to brain morphology and function may be exacerbated in aging individuals who drink alcohol to excess. The neuroimmune response to alcohol in aging is complex. The few studies investigating this issue have reported heightened basal activity and either hypo- or hyper-reactivity to an alcohol challenge. This review of preclinical research will first introduce key players of the immune system, then explore changes in neuroimmune function with aging or alcohol alone, with discussion of vulnerable brain regions, changes in cytokines, and varied reactions of microglia and astrocytes. We will then consider different levels of alcohol exposure, relevant animal models of AUD, and neuroimmune activation by alcohol across the lifespan. By identifying key findings, challenges, and targets for future research, we hope to bring more attention and resources to this underexplored area of inquiry.

The interplay between sperm-mediated and care-mediated paternal effects in threespine sticklebacks

The environment experienced by one generation can influence the phenotypes of future generations. Because parental cues can be conveyed to offspring at multiple points in time, ranging from fertilization to posthatching/parturition, offspring can potentially receive multiple cues from their parents via different mechanisms. We have relatively little information regarding how different mechanisms operate in isolation and in tandem, but it is possible, for example, that offspring phenotypes induced by nongenetic changes to gametes may be amplified by, mitigated by, or depend upon parental care. Here, we manipulated paternal experience with predation risk prior to fertilization in threespine stickleback, Gasterosteus aculeatus, and then examined the potential of paternal care to mitigate and/or amplify sperm-mediated paternal effects. Specifically, we compared (1) offspring of predator-exposed fathers who were reared without paternal care, (2) offspring of predator-exposed fathers who were reared with paternal care, (3) offspring of control (unexposed) fathers who were reared without paternal care and (4) offspring of control fathers who were reared with paternal care. We found that offspring of predator-exposed fathers were less active and had higher cortisol following a simulated predator attack. Although predator-exposed males shifted their paternal care behaviours - reduced fanning early in egg development and increased fanning right before egg hatching compared to control males - this shift in paternal behavior did not appear to affect offspring traits. This suggests that paternal care neither amplifies nor compensates for these phenotypic effects induced by sperm and that nongenetic changes induced by sperm may occur independently of nongenetic changes induced by paternal care. Overall, these results underscore the importance of considering how parents may have multiple nongenetic mechanisms by which they can influence offspring.

κ-Opioid receptor antagonism reverses heroin withdrawal-induced hyperalgesia in male and female rats

Although opioids are potent analgesics, a consequence of chronic opioid use is hyperalgesia during withdrawal, which may contribute to opioid misuse. Dynorphin, the endogenous ligand of κ-opioid receptors (KORs), is upregulated in opioid-dependent rats and in animal models of chronic pain. However, the role of KORs in opioid withdrawal-induced hyperalgesia remains to be determined. We hypothesized that KOR antagonism would reverse opioid withdrawal-induced hyperalgesia in opioid-dependent rats. Male and female Wistar rats received daily injections of heroin (2-6 mg/kg, SC) and were tested for mechanical sensitivity in the electronic von Frey test 4-6 h into withdrawal. Female rats required significantly more heroin than male rats to reach comparable levels of both heroin-induced analgesia and hyperalgesia (6 mg/kg vs. 2 mg/kg). Once hyperalgesia was established, we tested the effects of the KOR antagonists nor-binaltorphimine (norBNI; 30 mg/kg, SC) and 5'-guanidinonaltrindole (5'GNTI; 30 mg/kg, SC). When the animals continued to receive their daily heroin treatment (or saline treatment in the repeated saline group) five times per week throughout the experiment, both KOR antagonists reversed heroin withdrawal-induced hyperalgesia. The anti-hyperalgesia effect of norBNI was more prolonged in males than in females (14 days vs. 7 days), whereas 5'GNTI had more prolonged effects in females than in males (14 days vs. 4 days). The behavioral effects of 5'GNTI coincided with higher 5'GNTI levels in the brain than in plasma when measured at 24 h, whereas 5'GNTI did not reverse hyperalgesia at 30 min posttreatment when 5'GNTI levels were higher in plasma than in the brain. Finally, we tested the effects of 5'GNTI on naloxone-induced and spontaneous signs of opioid withdrawal and found no effect in either male or female rats. These findings indicate a functional role for KORs in heroin withdrawal-induced hyperalgesia that is observed in rats of both sexes.

Sex-specific plasticity across generations II: Grandpaternal effects are lineage specific and sex specific

Transgenerational plasticity (TGP) occurs when the environment encountered by one generation (F0) alters the phenotypes of one or more future generations (e.g. F1 and F2). Sex selective TGP, via specific lineages or to only male or female descendants, has been underexplored in natural systems, and may be adaptive if it allows past generations to fine-tune the phenotypes of future generations in response to sex-specific life-history strategies. We sought to understand if exposing males to predation risk can influence grandoffspring via sperm in three-spined stickleback Gasterosteus aculeatus. We specifically tested the hypothesis that grandparental effects are transmitted in a sex-specific way down the male lineage, from paternal grandfathers to F2 males. We reared F1 offspring of unexposed and predator-exposed F0 males under 'control' conditions and used them to generate F2s with control grandfathers, a predator-exposed maternal grandfather (i.e. predator-exposed F0 males to F1 daughters to F2s), a predator-exposed paternal grandfather (i.e. predator-exposed F0 males to F1 sons to F2s) or two predator-exposed grandfathers. We then assayed male and female F2s for a variety of traits related to antipredator defence. We found little evidence that transgenerational effects were mediated to only male descendants via the paternal lineage. Instead, grandpaternal effects depended on lineage and were mediated largely across sexes, from F1 males to F2 females and from F1 females to F2 males. When their paternal grandfather was exposed to predation risk, female F2s were heavier and showed a reduced change in behaviour in response to a simulated predator attack relative to grandoffspring of control, unexposed grandparents. In contrast, male F2s showed reduced antipredator behaviour when their maternal grandfather was exposed to predation risk. However, these patterns were only evident when one grandfather, but not both grandfathers, was exposed to predation risk, suggesting the potential for non-additive interactions across lineages. If sex-specific and lineage effects are common, then grandparental effects are likely underestimated in the literature. These results draw attention to the importance of sex-selective inheritance of environmental effects and raise new questions about the proximate and ultimate causes of selective transmission across generations.

Complications after two transphyseal bridging techniques for treatment of angular limb deformities of the distal radius in 568 Thoroughbred yearlings

REASONS FOR PERFORMING STUDY

Surgical correction of carpal angular limb deformities by growth retardation is commonly undertaken with a screws and tension band wire loop technique (S&W) or a single transphyseal screw (STS). This study compares complications after S&W and STS bridging in the distal radius of Thoroughbred yearlings.

OBJECTIVE

To compare the prevalence of complications serious enough to require follow-up radiographs following either S&W or STS surgery for growth manipulation in the distal radius of Thoroughbred yearlings.

METHODS

Medical records and radiographs from Thoroughbred yearlings (age range 261-457 days) treated for carpal angular limb deformities at a single hospital over 2 years were reviewed. Each of the techniques was used exclusively during a single year. The complication threshold criterion for inclusion was the need for nonroutine radiographs of the operated site anytime after implant insertion or removal.

RESULTS

Of 568 horses, 253 received S&W and 315 received STS. Horses were of similar age at the time of surgery for STS and S&W. Single transphyseal screws were left in place for a significantly shorter amount of time (16 days). Sex, the limb(s) treated and medial vs. lateral placement were not significantly different between techniques. Complications included physitis post implant removal, metaphyseal collapse post implant removal, infection, overcorrection and seroma formation severe enough to require radiography. Physitis and metaphyseal collapse occurred significantly more frequently with STS compared with S&W. Infection, overcorrection and seromas were not significantly different between techniques.

CONCLUSION

The STS and S&W techniques are both viable treatment options for correction of carpal angular limb deformities. However, horses treated with the STS technique have a significantly increased risk of developing physitis or metaphyseal collapse.

POTENTIAL RELEVANCE

Horses treated with STS bridging have a significantly increased risk of developing the post correction complications of moderate to severe physitis and metaphyseal collapse compared with horses treated with S&W bridging.

Neu entwickeltes Kiefergelenkkopfimplantat zur temporären Kondylus-Rekonstruktion in der ablativen Tumorchirurgie

BACKGROUND

Based on own retrospective studies a condylar head add-on system for immediate, temporary reconstruction in patients undergoing ablative surgery requiring the removal of the manibular condyle has been developed in cooperation with the Department of Oral and Maxillofacial Surgery of the University of Tennessee, USA, and the Association for the Study of Internal Fixation (AO/ASIF).

PURPOSE

The design of the new condylar head add-on system and its use in an anatomical dissection study on a human cadaver are introduced and discussed. DESIGN AND FIRST EXPERIENCES: The condylar replacement is made of commercial pure titanium and is conceived as an add-on system. It consists of a reconstruction plate (2.4 Uni-LOCK-System) und an adaptable condylar head that can be fitted on either side. The offset of the condylar head in a medial direction allows anatomically correct positioning of the implant. The slanted oval head shall provide a large contact area while maintaining function of the mandibular joint. The height-adjustable positioning of the condylar head add-on with four different fixations plates facilitates an intraoperative vertical correction of the condylar head without necessary bending of a new reconstruction plate. A condylar head add-on used on both sides and combined with the frequently used 2.4 Uni-LOCK-plate benefits from reduced storekeeping and turns out to be advantageous from an economic point of view.

PERSPECTIVE

An international, prospective multi-center study evaluating the intraoperative applicability of the new condylar head add-on system and its functional as well as aesthetic results during the first two postoperative years has started in September 2006.

Bone grafting the jaws in the 21st century: the use of platelet-rich plasma and bone morphogenetic protein

The use of PRP and rhBMP-2 in facial skeletal reconstruction is supported by theoretical and practical human and animal data that represent exciting prospects for the 21st century. Although the use of PRP in conjunction with autogenous grafting of the maxillofacial complex increases the already impressive predictability of this technique, it is possible that improvement of the clinical use of rhBMP-2 may one day obviate the need for a donor site harvest of bone.

Platelet-rich plasma: Growth factor enhancement for bone grafts

Platelet-rich plasma is an autologous source of platelet-derived growth factor and transforming growth factor beta that is obtained by sequestering and concentrating platelets by gradient density centrifugation. This technique produced a concentration of human platelets of 338% and identified platelet-derived growth factor and transforming growth factor beta within them. Monoclonal antibody assessment of cancellous cellular marrow grafts demonstrated cells that were capable of responding to the growth factors by bearing cell membrane receptors. The additional amounts of these growth factors obtained by adding platelet-rich plasma to grafts evidenced a radiographic maturation rate 1.62 to 2.16 times that of grafts without platelet-rich plasma. As assessed by histomorphometry, there was also a greater bone density in grafts in which platelet-rich plasma was added (74.0% +/- 11%) than in grafts in which platelet-rich plasma was not added (55.1% +/- 8%; p = 0.005).

Platelet-rich plasma: Growth factor enhancement for bone grafts

Platelet-rich plasma is an autologous source of platelet-derived growth factor and transforming growth factor beta that is obtained by sequestering and concentrating platelets by gradient density centrifugation. This technique produced a concentration of human platelets of 338% and identified platelet-derived growth factor and transforming growth factor beta within them. Monoclonal antibody assessment of cancellous cellular marrow grafts demonstrated cells that were capable of responding to the growth factors by bearing cell membrane receptors. The additional amounts of these growth factors obtained by adding platelet-rich plasma to grafts evidenced a radiographic maturation rate 1.62 to 2.16 times that of grafts without platelet-rich plasma. As assessed by histomorphometry, there was also a greater bone density in grafts in which platelet-rich plasma was added (74.0% +/- 11%) than in grafts in which platelet-rich plasma was not added (55.1% +/- 8%; p = 0.005).

Accelerated fractionation radiotherapy and concomitant chemotherapy in patients with stage IV inoperable head and neck cancer

BACKGROUND

Stage IV inoperable head and neck cancer has a 2-year mortality rate of greater than 70% when treated with conventional radiotherapy. A Phase II study was undertaken to evaluate the effects of concomitant chemotherapy and accelerated, interrupted, twice-a-day radiotherapy on tumor response, locoregional control, survival, and morbidity.

METHODS

Thirty-four patients with Stage IV inoperable squamous cell carcinoma of the head and neck and a minimum follow-up of 36 months were evaluated. Concomitant chemoradiotherapy was administered during weeks 1, 3, and 5 (with planned breaks during weeks 2 and 4), consisting of cisplatin 60 mg/m2 on day 1, continuous 5-day infusion of 5-fluorouracil, 750 mg/m2 per day, and radiotherapy, 2 Gy twice a day, more than 6 hours apart, followed by 3 days of radiation therapy alone (final "boost") in week 6, for a total dose of 70 Gy and treatment duration of 5 1/2 weeks (38 days).

RESULTS

Twenty-seven patients achieved a clinical complete response (82%). Actuarial locoregional control at 3 years was 73% and the actuarial 3-year survival probability, including all deaths, was 38%. All locoregional recurrences were manifested within 12 months. Of the 20 deaths, 12 were tumor related (locoregional and/or metastatic), 3 were treatment related, and 5 were due to other causes. Acute toxicity consisted of grade 3 mucositis and dysphagia and grade 2-3 leukopenia, not requiring treatment interruption or cessation.

CONCLUSION

Concomitant accelerated radiation therapy and chemotherapy is a feasible treatment approach in this prognostically poor patient population, yielding dramatic tumor responses and impressive locoregional control at the cost of somewhat increased acute toxicity. Although serious late complications have not been observed, caution should be exercised in view of the relatively short follow up.

The potential for HIV transmission through allogeneic bone. A review of risks and safety

Over the past two decades, oral and maxillofacial surgeons have gained a greater appreciation for the biology of allogeneic bone healing, resulting in a dramatic increase in its indications and use. Unfortunately, this time period has also ushered in near epidemic proportions of HIV-infected persons, some of whom might be considered as potential donors of allogeneic bone. As this article will discuss, surgeons and tissue bank teams alike must be aware of the clinical and serologic criteria associated with an acceptable donor. Only in this way can contamination-free specimens be obtained and surgically implanted.

Isolation of Actinomyces species and Eikenella corrodens from patients with chronic diffuse sclerosing osteomyelitis

Cultures from 26 patients with chronic diffuse sclerosing osteomyelitis of the mandible were studied. In most cases there was a mutualistic infection involving any one of the known human Actinomyces species together with Eikenella corrodens. In a few cases, Arachnia species were substituted for Actinomyces and gram-negative anaerobes for E corrodens. The specific culture protocol used to identify these organisms from clinical specimens is described. Taxonomic and experimental evidence that supports an infectious etiology are presented.

Tissue banking safety: caveats and precautions for the oral and maxillofacial surgeon

Oral and maxillofacial reconstructive surgeons using allogeneic tissues have expressed justifiable concern over the safety of these tissues as they relate to the transmission of infectious disease. This report reviews cases of infectious disease transmission from inadequately screened donors of allogeneic tissues, as well as those related to improper sterilization and cataloging of these tissues. It is concluded that good judgment and attention to good science on the part of the tissue bank as well as the surgeon can maximize the ability to place contamination-free specimens, thereby avoiding complications similar to those described.

Myospherulosis. Complicating wound healing

Myospherulosis is a complication of wound healing which results from an action between lipids and extravasated erythrocytes. A case of myospherulosis of the mandible is reviewed with its history, histopathology and occurrence.

Creutzfeldt-Jakob disease from allogeneic dura: a review of risks and safety

Surgeons and the lay public have recently expressed concern over the safety of allogeneic dura as it relates to the transmission of Creutzfeldt-Jakob Disease. Indeed, two cases have resulted from use of tissue procured from a commercial agency that did not adhere to criteria accepted by the American Association of Tissue Banks or the Southeast Organ Procurement Foundation. This review discusses the risks and safety of allogeneic dura. The findings should reassure the surgeon of the safety of allogeneic dura when it is properly processed and catalogued by a bona fide, reputable tissue bank. To date, there have been no documented cases reported to the Center for Disease Control in which Creutzfeldt-Jakob Disease was transmitted from allogeneic dura obtained from a registered tissue bank.

Polycythemia vera in an oral surgical patient. A case report

Polycythemia vera is a stem cell disorder that results in an increase in the production of red blood cells. Although numerous mechanisms have been suggested, the cause of the disease is unknown. Diagnosis is based on clinical and laboratory presentation. This article reviews the history of polycythemia vera and illustrates a representative case report of the disease process. Postoperative morbidity in the surgical patient is discussed with respect to preoperative therapeutic control. Recommendations are made for preoperative therapy in patients undergoing oral and maxillofacial surgery.

A retrospective study of untreated orbital blow-out fractures

A retrospective study of 27 cases of untreated orbital blow-out fractures is presented. These patients were managed non-surgically because they presented with minimal ophthalmologic symptoms, or they sustained other injuries that prevented early repair. Twelve patients returned for follow-up examination and eight were contacted by telephone. In evaluating patients for diplopia, enophthalmos, hypesthesia, and restricted ocular movement, 85% showed complete resolution of symptoms. Based on these findings, surgical intervention is recommended only in those patients who demonstrate residual diplopia in primary gaze and restricted ocular motility that persist after 10 to 14 days, the presence of enophthalmos greater than 2 mm, and gross disruption of the orbital floor as confirmed by CT or tomography.

Circulating lupus anticoagulant in a surgical temporomandibular joint patient. Report of a case

The lupus anticoagulant is a unique inhibitor of hemostasis. Its occurrence in patients with systemic lupus erythematosus reportedly varies from 5% to 50%. The inhibitor is endogenously produced and occurs in a diverse number of clinical states. The present case report reviews an inadvertent discovery of circulating lupus anticoagulant in a patient scheduled for surgery of the temporomandibular joint.

Inhibition of calcium phosphate precipitation by human salivary acidic proline-rich proteins: structure-activity relationships

Absence of precipitation of calcium phosphate salts onto tooth surfaces from human saliva, which is supersaturated with respect to calcium phosphate salts, has been attributed in part to the presence in the salivary secretions of a group of acidic proline-rich phosphoproteins (PRP). These macromolecules are considered to act by adsorbing onto dental enamel where they inhibit surface-induced precipitation of calcium phosphate salts. The inhibitory activity is known to be associated primarily with the amino-terminal region of the PRP. The aim of this study was to determine the features of the primary structure of this molecular segment responsible for inhibitory activity. The 30-residue, amino-terminal segment of PRP-3, which contains the two phosphoserines and 11 of the 13 carboxyl groups present in PRP-3, was obtained by tryptic digestion. This peptide, designated PRP-3(TI), was treated with thermolysin to give the monophosphopeptides, Val-PSer-Gln-Glu-Asp-Val-Pro and Leu-Val-Ile-Ser-Asp-Gly-Gly-Asp-PSer-Glu-Gln, and with alkaline phosphatase to give the dephosphorylated analog, PRP-3(TI)DP. The inhibitory activities of PRP-3(TI) and the derived peptides, a synthetic peptide, phosphoseryl-phosphoserine (PSer-PSer), and O-phosphoserine (PSer), were determined using an assay based on inhibition of seeded precipitation of calcium phosphate. Inhibitory activities, expressed as concentrations of inhibitors required to give standard inhibitory activities, were PRP-3(TI), 0.59 microM; PSer-PSer, 3.5 microM; the two monophosphopeptides, 29 and 32.5 microM; PRP-3(TI)DP, 56 microM; PSer, 329 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Chlorine Oxide in the Stratospheric Ozone Layer: Ground-Based Detection and Measurement

Stratospheric chlorine oxide, a significant intermediate product in the catalytic destruction of ozone by atomic chlorine, has been detected and measured by a ground-based 204-gigahertz, millimeter-wave receiver. Data taken at latitude 42 degrees N on 17 days between 10 January and 18 February 1980 yield an average chlorine oxide column density of approximately 1.05 x 10(14) per square centimeter or approximately 2/3 that of the average of eight in situ balloon flight measurements (excluding the anomalously high data of 14 July 1977) made over the past 4 years at 32 degrees N. We find less chlorine oxide below 35 kilometers and a larger vertical gradient than predicted by theoretical models of the stratospheric ozone layer.