Evaluation of an independent prestin mouse model derived from the 129S1 strain.

Studies using the prestin knockout mouse indicate that removal of the outer hair cell (OHC) motor protein is associated with loss of sensitivity, frequency selectivity and somatic electromotility. Here we provide data obtained from another prestin mouse model that was produced commercially. In vivo electrical recordings from the round window indicate that the phenotype is similar to that of the original knockout generated by the Zuo group at St. Jude Children's Research Hospital. Hence, compound action potential (CAP) thresholds are shifted in a frequency-dependent manner and CAP tuning curves at 12 kHz are flat for masker frequencies between 3 and 18 kHz. Although CAP input-output functions at 6 kHz show a shift in sensitivity at low levels, responses approach wild-type magnitudes at high levels where the cochlear amplifier has less influence. In order to confirm that the loss of sensitivity and frequency selectivity is due to loss of prestin, we performed immunohistochemistry using a prestin antibody. Cochlear segments from homozygous mutant mice showed no fluorescence, while wild-type mice displayed a fluorescent signal targeted to the OHC's lateral membrane. Absence of prestin protein was confirmed using LDS-PAGE/Western blot analysis. These results indicate that the loss of function phenotype is associated with loss of prestin protein. Lack of prestin protein also results in a shortening of OHC length to approximately 60% of wild-type, similar to that reported previously by Liberman's group. The linkage shown between the loss of prestin protein and abnormal cochlear function validates the original knockout and attests to the importance of OHC motor function in the auditory periphery.

The role of gravity in gentamicin-induced toxic effects in a rabbit model.

OBJECTIVE: To define the role of gravity in gentamicin sulfate-induced retinal toxic effects by injecting the drug into vitrectomized rabbit eyes oriented in one of two positions. METHODS: Ten right eyes of New Zealand white rabbits underwent a two-port pars plana vitrectomy and were positioned with traction scleral sutures to rotate the medullary ray superiorly (five eyes) or nasally (five eyes). Six eyes received a pars plana intravitreal injection of 400 micrograms (0.1 mL) of gentamicin, and four eyes received 0.1 mL of balanced salt solution only. All eyes were kept in position for 30 minutes after the injection. Unoperated-on fellow eyes served as controls. Three or 5 days later, the eyes were enucleated and histopathologic examination was performed. RESULTS: Light and electron microscopy of gentamicin-treated eyes showed inner-retinal edema and disruption of the nerve-fiber and ganglion-cell layers within the more dependent retina vs sparing of the less dependent half of the retina. Eyes that received balanced salt solution showed rare inflammatory cells along the inner-retinal surface but essentially no inner-layer disruption. Examination of unoperated-on control eyes showed no inflammatory cells, edema, or necrosis. CONCLUSION: Gravitational effects and positioning contribute to the location of gentamicin-induced retinal toxic effects in vitrectomized eyes.

Contribution of arterial blood lactate measurement to the care of critically ill patients.

Arterial blood samples from 202 critically ill patients were studied. Lactate concentration, PO2, PCO2, pH, oxygen saturation, total CO2, and toe temperature were measured. Base excess, buffer base, actual bicarbonate, and standard bicarbonate were calculated. Analysis of the initial data obtained from each patient revealed that lactate concentration alone could not be used to predict survival. Elevations in lactate concentrations were observed in all types of acid-base disturbances. Survival was lowest (30%) for patients in metabolic acidosis with respiratory compensation, mean lactate concentration 10.5 mEq/l (mmol/l), and highest (65%) for patients in uncompensated respiratory alkalosis, mean lactate concentration, 2.57 mEq/l (mmol/l). Knowing the type of acid-base disturbance is necessary to evaluate the significance of elevated blood lactate values.

Computer-assisted differential diagnosis of laboratory abnormalities and follow-up testing. Evaluation of the accuracy of a computer program.

An evaluation is made of a computer program which generates a differential diagnostic list given a set of input data obtained from an admission chemistry screening profile. The program is tested by supplying input data on patients for whom diseases are known. The laboratory data from 367 patients are examined. Accurate computer diagnosis is obtained in many disease categories. The original computer program is modified to suggest the follow-up tests indicated based on the diagnoses it makes. By using this program and some additional clinical input from the physician, the clinical pathologist can select the most appropriate computer diagnosis and begin the follow-up testing. Accelerated diagnosis and patient care should result.

Erwinia chrysanthemi strains cause death of human gastrointestinal cells in culture and express an intimin-like protein.

The bacterium Erwinia chrysanthemi is a model plant pathogen, responsible for causing cell death in plant tissue. Cell-wall depolymerizing enzymes and avirulence proteins essential for parasitism by this bacterium utilize dedicated type II and type III secretion systems, respectively. Although E. chrysanthemi is not recognized as a mammalian pathogen, we have observed that the bacterium can adhere to, cause an oxidative stress response in and kill cultured human adenocarcinoma cells. These bacteria express a surface protein that bears immunological identity to intimin, a protein required for full virulence of enterohemorrhagic and enteropathogenic Escherichia coli. A type III secretion mutant of E. chrysanthemi was observed to have a significantly lower capability of causing death than the wild-type strain in parallel cultures of human colon adenocarcinoma cells. These observations suggest that E. chrysanthemi has the potential to parasitize mammalian hosts as well as plants.

Sleep structure following status epilepticus.

OBJECTIVES: To determine the effect of status epilepticus (SE) on sleep. BACKGROUND: SE has a high incidence of morbidity and mortality. The study of sleep structure following SE may have implications for recovery in these patients. METHODS: Twenty-four hour polysomnography was recorded in a 52-year-old patient following generalized convulsive SE not complicated by other medical or neurologic conditions. Another patient with no known history of seizures was recorded under similar conditions. RESULTS: The first day following SE was associated with markedly abnormal sleep structure, consisting largely of stage 1 with minimal slow wave or REM sleep. Over 4 days, slow wave and REM returned to normal values and no rebound was seen. The control patient demonstrated normal sleep parameters for their age, demonstrating that sleep disruption was not due to recording conditions alone. CONCLUSIONS: This case demonstrates that sleep structure is markedly abnormal following generalized convulsive SE. As sleep may serve a restorative function, improving sleep postictally may hasten or improve recovery. Larger studies will be required to determine whether this is a common finding in such patients, and whether outcome is associated with improved sleep quality.

Premedication for the pediatric patient: new and old drugs.

Over the last 15 years a rapid growth has occurred in the number of pediatric patients that are encountered in the operating room. A developing sophistication on the part of both children and parents, coupled with a rapidly expanding recognition of the need to minimize the amount of physical and psychological trauma that a child has to experience, has led to a growing use of premedication agents for children. A review of the premedication agents currently in use, their various routes of administration, as well as their associated benefits and risks, is presented.

The presence of nuclear and mitochondrial uracil-DNA glycosylase in extracts of human KB cells.

Extracts of human KB cells contain detectable uracil-DNA glycosylase activity. The majority of the activity is located within the nuclear fraction, however we present evidence for the presence of identifiable uracil-DNA glycosylase activity associated with the mitochondrial fraction of these cells.

What methods of pediatric pain management can be incorporated into a generalist's anesthesia practice?

Historically, pain in ill and injured pediatric patients has not been recognized or attended to. Subsequently, children often suffer in silence. Caretakers are often fearful to intervene aggressively to alleviate pain. A critical evaluation and integrative approach to the treatment of pediatric pain has only recently emerged, and curricula addressing the physiologic, behavioral, and biochemical differences related to pain has only recently been instituted in some medical schools and pediatric training programs. Children deserve special consideration in pain management since they may not be capable of comprehending the need for painful procedures and may not have learned strategies to cope with them. The importance of a comprehensive evaluation can not be overstated. The anesthetist can be of great assistance in pain management of the pediatric surgical patient by assessing his patient's postoperative pain needs and planning his/her anesthetic technique and recovery room course accordingly. Research in pediatric pain is still in its infancy, with crucial issues yet to be addressed. One of the most important is how to individualize the treatment of pain. We also need to learn more about children's natural coping styles and how parents and health care providers can enhance their effectiveness in contributing to the therapeutic team. It is hoped that readers will notice their patient's behaviors a little more closely, think about the extent of their private suffering, and become willing to offer a more studied, justifiable, and aggressive approach to pediatric pain management.

Ultramicro analysis for copper, cadmium, and zinc in human liver tissue by use of atomic absorption spectrophotometry and the heated graphite tube atomizer.

We describe a method of analysis for copper, cadmium, and zinc in a 15-mg (wet weight) sample of human liver by atomic absorption spectrophotometry. The sample is digested with nitric acid (1.0 mol/liter), evaporated, and dilute HNO3 (10 mmol/liter) added. The reconstituted acid mixture is injected into the graphite tube atomizer for analysis of Cu and Cd and aspirated into the air--acetylene flame for measurement of Zn. The absorbance for each metal is suppressed with increasing pH. NaNO3, KNO3, KCl, and NaCl (e.g.) quench the Cd absorbance in acid solutions that contain no protein, but not in the presence of protein. Metal ions added to the predigestion human liver sample at 10 percent and 100 percent of the intrinsic metal concentrations were, respectively, 93 percent and 90 percent accounted for analytically in the case of Cu, 98 percent and 102 percent for Zn, and 101 percent and 93 percent for Cd. Analysis of a National Bureau of Standards' Bovine Liver Standard Reference Material yielded results corresponding to 99 percent (Cu), 112 percent (Zn), and 91 percent (Cd) of the mean expected concentrations of these metals. The between-run coefficient of variation for the bovine liver material was 6 percent for Cu, 9 percent for Zn, and 10 percent for Cd. For 16 histologically normal samples of human liver, the mean values were: Cu, 26; Zn, 293; and Cd, 6.0 nanograms of metal per milligram dry weight, in agreement with values published previously. The method can be easily and reliably applied to small samples of liver obtained by closed-needle biopsy.

Carbon dioxide kinetics and capnography during critical care.

Greater understanding of the pathophysiology of carbon dioxide kinetics during steady and nonsteady state should improve, we believe, clinical care during intensive care treatment. Capnography and the measurement of end-tidal partial pressure of carbon dioxide (PETCO2) will gradually be augmented by relatively new measurement methodology, including the volume of carbon dioxide exhaled per breath (VCO2,br) and average alveolar expired PCO2. Future directions include the study of oxygen kinetics.

The multi-test system: a standardized approach to evaluation of delayed hypersensitivity and cell-mediated immunity.

While delayed cutaneous hypersensitivity (DCH) testing with ubiquitous antigens is acknowledged to be useful in assessment of cell mediated immunity, existing methods suffer from lack of standardized antigens and optimal doses. The authors have evaluated a new plastic, disposable device (Multi-Test, Lincoln Laboratories) for simultaneous administration of up to eight test materials by multiple puncture and seven ubiquitous antigens in 70% glycerol prepared by Institut Merieux. Each antigen was standardized chemically and biologically for DCH activity. The Multi-Test system proved to be safe, rapid, painless, and reproducible means of evaluating DCH to multiple standardized antigens. This procedure offers the potential for detecting changes in cell-mediated immunity in diseases individuals who are skin tested periodically.

Positron emission tomography study of regional cerebral metabolism in humans during isoflurane anesthesia.

BACKGROUND: Although the anesthetic effects of the intravenous anesthetic agent propofol have been studied in the living human brain using brain imaging technology, the nature of the anesthetic state evident in the human brain during inhalational anesthesia remains unknown. To examine this issue, the authors studied the effects of isoflurane anesthesia on human cerebral glucose metabolism using positron emission tomography (PET). METHODS: Five volunteers each underwent two PET scans; one scan assessed awake-baseline metabolism and the other scan assessed metabolism during isoflurane anesthesia titrated to the point of unresponsiveness (means +/- SD; expired = 0.5 +/- 0.1%). Scans were obtained with a GE2048 scanner (4.5-mm resolution-FWHM) using the 18fluorodeoxyglucose technique. RESULTS: Awake whole-brain glucose metabolism averaged 6.9 +/- 1.5 mg.100 g-1.min-1 (means +/- SD). Isoflurane reduced whole-brain metabolism 46 +/- 11% to 3.6 +/- 0.3 mg.100 g-1.min-1 (P < or = 0.005). Regional metabolism decreased fairly uniformly throughout the brain, and no evidence of any regional metabolic increases were found in any brain region for any participant. A region-of-interest analysis showed that the pattern of regional metabolism evident during isoflurane anesthesia was not significantly different from that seen when participants were awake. CONCLUSION: These data clarify that the anesthetic state evident in the living human brain during unresponsiveness induced with isoflurane is associated with a global, fairly uniform, whole-brain glucose metabolic reduction of 46 +/- 11%.

Severe combined immunodeficiency with cartilage-hair hypoplasa: in vitro response to thymosin and attempted reconstitution.

The present report describes an infant with severe combined immunodeficiency and cartilage-hair hypoplasia whose lymphocytes responded to thymosin in vitro. Immunologic evaluation was undertaken at 4 1/2 months of age following a history of recurrent severe infection. Family history included three cousins who died in early infancy, one from streptococcal meningitis and pneumonia, one from generalized varicella, and another from reticuloendotheliosis. Quantitative immunoglobulins were markedly depressed: IgG 141, IgA 0, and IgM 24 mg/100 ml. There was an absolute lymphopenia, multiple skin tests were negative, and in vitro lymphocyte responses to mitogens and antigens were depressed. Spontaneous E rosette determinations were 21% compared with control values of 65.7%. Erythrocyte adenosine deaminase (ADA) activity was normal. The patient's E rosette formation increased in the presence of thymosin, fraction 5, reaching a maximum of 56% with a concentration of 500 mug thymosin. Blastogenic responses to phytohemagglutinin also increased in the presence of thymosin. Transplantation of 24-week fetal thymus in Millipore diffusion chambers and subsequently transplantation of 18-week fetal thymus by intraperitoneal injection was accomplished. E rosettes increased to 35-40% and blastogenic responses to mitogens increased. Eight days after the second transplant the patient underwent a mild graft vs. host reaction which subsided after 1 week and mitogen blastogenic responses again increased to 5-8 times previous values, but still well below control ranges. Repeated episodes of pulmonary infection ensued, cor pulmonale resulted, and the clinical course was relentlessly downhill with the patient expiring from respiratory failure 5 months after transplantation.

The literature and perspectives on muscle relaxants for rapid sequence induction.

Since the advent of surgical anesthesia, one of the single greatest challenges to providers and researchers has been to develop, test, and promote drugs and techniques to facilitate rapid intubation and security of the airway to diminish risk of regurgitation and gastric aspiration. This article provides a comprehensive, historical perspective of such efforts, including the efficacy of various techniques and muscle relaxant drugs that have been used to further the ideal situation in which airway control would obviate the all-too-common morbidity statistics of gastric aspiration. Special emphasis is given to the review of succinylcholine and vecuronium relative to their roles in rapid sequence induction.