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Biomedical subjects

M A Novak

Publications and source records attributed to M A Novak.

At least 37 records · Page 2Linked to original sources
PubMed1993

Sex and species differences in the vasopressin innervation of sexually naive and parental prairie voles, Microtus ochrogaster and meadow voles, Microtus pennsylvanicus.

To study whether central systems that are implicated in functions associated with reproduction show different changes in males and females that become parental, the central vasopressin (AVP) innervation was compared in two species of voles: prairie voles, in which males and females provide parental care, and meadow voles, in which only females provide parental care. For both species, the densities of AVP-immunoreactive (AVP-ir) fibers in the lateral septum, lateral habenular nucleus, medial preoptic area and paraventricular nucleus of the thalamus were compared in males and females that were sexually inexperienced or had become parents 6 days before sacrifice. The lateral septum and lateral habenular nucleus presumably receive their projections from the bed nucleus of the stria terminalis and medial amygdaloid nucleus, while the other two areas presumably receive their projections from the suprachiasmatic nucleus. Differences between sexually naive and parental animals were found only in the presumed projections of the bed nucleus of the stria terminalis and medial amygdaloid nucleus. In both species, AVP-ir fiber densities in the lateral habenular nucleus and the lateral septum were much greater in males than in females regardless of parental state. In prairie voles, AVP-ir fiber density in the lateral septum and lateral habenular nucleus was reduced in parental males, while no differences were found in females. In parental meadow voles, the AVP-ir fiber density in the lateral septum did not show changes, while the fiber density in the lateral habenular nucleus was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Auditory performance of children with cochlear ossification and partial implant insertion.

The management of the profoundly deaf child with a cochlear implant poses a special challenge, particularly when total ossification of the cochlea is present. In this setting, insertion of an electrode array into a child's cochlea is often difficult. Our experience supports the feasibility of partial insertion of a multichannel implant into the basal turn of an ossified cochlea. Five children with ossified cochleae who had undergone partial implantation of a multichannel electrode were compared with the performance of matched controls who had full insertion of multichannel implants. No dramatic differences were detected during a 6- to 18-month follow-up period on selected test measures. These preliminary results suggest that active electrode number may exert a limited effect on performance with a cochlear implant. Drilling out the basal turn of an ossified cochlea in conjunction with partial insertion of a multichannel implant appears to be an acceptable surgical and rehabilitational alternative for placement of a cochlear implant prosthesis in children with complete cochlear ossification.

Adolescent↗
PubMed1991

Do rhesus monkeys (Macaca mulatta) attribute knowledge and ignorance to others?

The ability of 4 rhesus monkeys (Macaca mulatta) to understand the causal connection between seeing and knowing was investigated. The subjects were tested to determine if they could discriminate between information provided by experimenters who randomly alternated between roles of guesser and knower. In a series of tests, the knower either hid food under 1 of 3 cups or watched as someone else hid the food. The guesser waited outside the room or covered her or his head until the food was hidden. The subjects watched this procedure occur but could not see which cup the food was hidden under. The knower pointed to the correct cup while the guesser pointed to an incorrect one. None of the macaques provided any evidence that they realized the different states of knowledge possessed by the guesser and knower. The results are consistent with the hypothesis that rhesus macaques are incapable of making inferences about the mental states of others.

Animals↗
PubMed1991

Problem solving in elderly sophisticated and naive monkeys.

Elderly (greater than 23 years) rhesus monkeys, some of whom had previous learning test experience, were tested on a standardized battery of discrimination and concept-formation tasks, and their performance was compared with that of test-naive middle-aged (15 years) and juvenile (2 years) monkeys. Naive elderly monkeys performed more poorly on virtually all tasks compared to their younger counterparts. In contrast, test-experienced elderly monkeys outperformed both middle-aged and juvenile monkeys on those problem types with which they had limited previous experience, despite the fact that 8-10 years had passed since their prior training. However, test-experienced elderly monkeys did not display superior performance on new tests that approximated visual acuity or assessed delayed discrimination capabilities.

Aging↗
PubMed1991

Independent evaluation of the speech perception abilities of children with the Nucleus 22-channel cochlear implant system.

The performance of 28 children with the Nucleus multi-channel cochlear implant, who had used the device an average of 1.7 yr, was examined on a battery of speech perception measures. All children demonstrated better speech perception skills with the implant than they had in the preimplant condition with hearing aids. With the Nucleus implant, 61% of the children demonstrated some open-set speech recognition and another 14% demonstrated closed-set speech recognition. Scores on the tests were corrected for guessing and a hierarchy of test difficulty was developed. The results revealed systematic differences in performance as a function of perception task and test format. The results of regression analyses, which were performed to identify predictors of success, showed that communication mode made a significant unique contribution to the variance in performance among subjects on an open-set word recognition test. When the scores of the children who used oral or total communication were compared on the full battery of tests, however, there were few significant group differences.

Adolescent↗
PubMed1991

Social interaction in nonhuman primates: an underlying theme for primate research.

Social living is assumed to be a critical feature of nonhuman primate existence inasmuch as most primate species live in social groups in nature. Recent USDA legislation emphasizes the importance of social contact in promoting psychological well-being and recommends that laboratory primates be housed with companions when consistent with research protocols. Our goals were to examine the link between social housing and psychological well-being and to explore the idea that research may be compromised when primates are studied in environments that vary too greatly from their natural ecological setting (individual cage housing versus group housing). Three general points emerge from these examinations. First, providing companionship may be a very potent way in which to promote psychological well-being in nonhuman primates; however, social living is not synonymous with well-being. The extent to which social housing promotes psychological well-being can vary across species and among individual members of the same species (for example, high- and low-ranking monkeys). Secondly, housing conditions can affect research outcomes in that group-housed animals may differ from individually housed animals in response to some manipulation. Social interaction may be a significant variable in regulating the biobehavioral responses of nonhuman primates to experimental manipulations. Finally, a larger number of socially housed subjects than individually housed subjects may be necessary for some biomedical research projects to yield adequate data analysis. Thus, social living has significant benefits and some potential costs not only for the animals themselves, but for the research enterprise.

Animals↗
PubMed1991

Prediction of auditory nerve survival in humans using the electrical auditory brainstem response.

This investigation studied the electrical auditory brainstem response (EABR) input-output functions in three groups of patients: individuals with normal auditory neural systems; patients with acquired, profound sensorineural hearing loss; and patients with congenital, profound sensorineural hearing loss. Each input-output function was obtained in the operating room under general anesthesia and with the patient paralyzed to eliminate myogenic contamination. In contrast to the acoustically elicited ABR, the EABR waveforms were characterized by a dominant early wave corresponding in latency to wave II. This wave was much larger and often appeared at lower stimulus intensities than wave V. The results, plotted according to rate of growth for waves II and V, showed that normal subjects generally had larger, more robust early waves than either hearing impaired group. Little difference was noted in the amplitudes or rates of growth for wave V among the three groups. Based on these observations, we concluded that the EABR demonstrated differences in the way normal and impaired systems respond to electrical stimulation. In addition, the EABR may be useful in providing a qualitative prediction of neural survival into broad categories of many surviving neurons versus a marked reduction in ganglion/neuronal density.

Adolescent↗
PubMed1990

Labyrinthine ossification after meningitis: its implications for cochlear implantation.

Labyrinthine ossification can be found in a high percentage of patients with profound deafness resulting from bacterial meningitis. Radiographic evidence of ossification can be found as early as 2 months after the acute infection, indicating that the intracochlear process probably begins much earlier. If long, intracochlear cochlear implants are to be most successfully used in these patients, an aggressive approach to clinical management following the meningitis should be taken. Illustrative case reports and suggested guidelines for evaluation and treatment are given.

Calcinosis↗
PubMed1990

Myogenic influences on the electrical auditory brainstem response (EABR) in humans.

Two cases demonstrating the effects of myogenic artifact on the electrical auditory brainstem response (EABR) when using a promontory stimulation site are presented. Intensity-response functions were obtained in the unparalyzed condition, then repeated after infusion of a neuromuscular paralyzing agent. In both cases, the myogenic response was observed at lower stimulus intensities than the EABR components. As intensity increased, the myogenic responses grew at extremely rapid rates and made any subsequent identification of auditory responses virtually impossible. To alleviate the adverse influence of myogenic components, general anesthesia and a paralyzing agent must be incorporated into the test protocol when acquiring the EABR using a promontory site of stimulation.

Atracurium↗
PubMed1989

Auditory brain-stem responses in children with previous otitis media.

The auditory brain-stem responses (ABRs) of 18 children who received tympanostomy tubes due to well-documented history of otitis media with effusion (OME) were compared with a matched control group with little or no history of effusion. The subjects in the OME group had significantly longer ABR latencies for waves III and V, with the most compelling delay for wave III and the III-I interwave interval. Although wave I prolongation in the OME group was not significant, the possible contribution of a peripheral effect on the latencies of waves III and V was investigated. The typical gender effect for the ABR latencies was unaltered in the OME group, and there was no group by gender interaction. We suggest that although the data support increased ABR latencies for children with a history of OME, they do not establish a causal relationship.

Acoustic Impedance Tests↗
PubMed1989

Recovery from OME-related phonologic delay following tube placement.

Subjects with documented histories of frequent or persistent otitis media with effusion (OME) who were judged to be below age level phonologically prior to placement of pressure equalization (PE) tubes were reassessed at 4-month intervals. Group A (n = 22) subjects caught up with their peers by the age of 4 years; Group B (n = 14) subjects' progress was delayed and phonologic intervention was advised. At initial testing the two groups were found to differ significantly in scores on postvocalic singleton obstruent omission, velar deviation, and stridency deletion. Elapsed time between initial diagnosis of OME and beginning of the first remission of 6 months or more also differed significantly, as did scores on the first phonologic reassessment. Subject scores on initial phonologic adequacy, retest adequacy, and elapsed time from diagnosis to remission appropriately classified all but 2 subjects by group. A formula is provided that appears to make early prediction of eventual need for phonologic intervention a practical possibility.

Articulation Disorders↗
PubMed1988

Calcium oxalate retinopathy associated with methoxyflurane abuse.

A 34-year-old woman developed a crystalline retinopathy after 2 years of inhalational abuse of methoxyflurane. After the woman developed renal failure, a renal biopsy showed multiple birefringent crystals in the renal tubular lumens, epithelial cells, and interstitium compatible with calcium oxalate. Multiple bright yellow-white crystals were deposited throughout the retina and at the level of the retinal pigment epithelium with a retinal arterial and periarterial predilection. This is the first reported case of methoxyflurane abuse with secondary hyperoxaluria in which there was a widespread retinal distribution of crystalline deposits, especially along the retinal arteries and arterioles.

Acute Kidney Injury↗
PubMed1987

Vacuum mixing of acrylic bone cement.

A partial-vacuum (500-550 mmHg), slow-speed (2 Hz) system for optimal blending of the liquid and powder components of Simplex-P acrylic bone cement was developed to eliminate five different sources of porosity observed with x-ray during the course of cement preparation and specimen fabrication. The vacuum mixing system produces set specimens of less than 1% porosity that have significant improvements over specimens prepared with conventional mixing in the mechanical properties of tensile and compressive strength and uniaxial tensile fatigue life. Hence, a much stronger cement can be available in surgery without any change in original chemical composition.

Bone Cements↗
PubMed1987

Predictors of phonologic inadequacy in young children prone to otitis media.

Children who have experienced recurrent or persistent otitis media with effusion (OME) at an early age often evidence deficient phonological skills in preschool that require remediation. If it were possible to identify these children before age 3, speech stimulation procedures and/or medical preventive measures might be considered. Forty children between the ages of 18 and 35 months who were scheduled for tympanostomy and tube placement were assessed audiologically and phonologically, data from their medical histories were tabulated, and parental educational and occupational status were determined. The subjects were reexamined at intervals of 3-4 months until their phonological performance reached a level indicating that broad phoneme-class or syllable-position remediation would not be necessary, or they had passed their third birthday. Discriminant analysis and multiple regression procedures indicated that certain measures or conditions, in combination, are good predictors of later phonologic inadequacy. Low age-weighted scores on production of velars, liquids, and postvocalic singleton obstruents, along with elevated thresholds at 500 Hz and a history of early onset and late remission from OME, were the most important variables characterizing children who did not catch up phonologically by age 3. Importantly, data from no one area alone could identify these children as reliably as combined data from the three areas.

Age Factors↗
PubMed1987

Krypton and argon laser photocoagulation for central serous chorioretinopathy.

Based on medical records, the authors divided 86 eyes of 84 patients with central serous chorioretinopathy with serous detachment of the macula and retinal pigment epithelial leakage on fluorescein angiography into three groups: no laser treatment (45 eyes), argon laser treatment (26 eyes), and krypton laser treatment (15 eyes). One or more episodes of recurrence developed during the follow-up period in 10 untreated eyes (22%), 9 argon-treated eyes (35%), and 0 krypton-treated eyes. The difference in recurrence rate between argon- and krypton-treated eyes was statistically significant. The findings suggest that whenever laser treatment is indicated, krypton red laser photocoagulation may reduce the incidence of recurrence in eyes with central serous chorioretinopathy.

Adult↗
PubMed1986

Divergent effects of early hydrocortisone treatment on behavioral and brain development in meadow and pine voles.

Developmental effects of a single hydrocortisone (HC) injection (80 micrograms/g on day 2 postnatal) were compared in two closely related species, meadow voles (Microtus pennsylvanicus) and pine voles (M. pinetorum). Effects of hormone administration were assessed in terms of the development of swimming behavior (head/nose position and front paw movement), alterations in social interactions (spatial location with respect to a stimulus animal), and by changes in somatic and brain growth. Although adult patterns of swimming behavior were found to be quantitatively different in meadow and pine voles, normal maturation in both species involved a progressive elevation of head/nose position along with a gradual inhibition of front paw movement. Compared with saline controls, HC-treated meadow voles showed an accelerated attainment of their adult pattern, whereas hormone-treated pine voles displayed a retardation in their swimming development. HC administration similarly led to increased body weights in developing meadow voles but decreased body weights in young pine voles. There was a tendency for hormone-treated meadow voles to spend more time near a stimulus animal than their control counterparts, whereas the opposite was observed for pine voles. In both species, the HC group displayed decreased cerebral and cerebellar weights in adulthood, whereas other organs were generally unaffected by hormone administration. Neurochemical analyses revealed no treatment effects or treatment by species interactions with respect to cerebral DNA levels. On the other hand, treated meadow voles but not pine voles showed an elevated concentration of sulfatide, a myelin-related lipid. These results are the first to demonstrate divergent behavioral and neurochemical effects of early glucocorticoid administration in closely related species studied under the same conditions. Furthermore, in accordance with earlier experiments on rats, swimming behavior was shown to be a useful measure for assessing changes in neuromuscular maturation.

Animals↗