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Biomedical subjects

S A Small

Publications and source records attributed to S A Small.

At least 19 recordsLinked to original sources
PubMed1999

Selective decline in memory function among healthy elderly.

OBJECTIVE: To use longitudinally acquired data to establish whether aging is associated with memory decline. BACKGROUND: Memory loss is one of the most frequent complaints among the elderly. Nevertheless, age-related memory decline remains controversial in large part because it has been established with cross-sectional studies. METHODS: A total of 212 community-based healthy people were followed prospectively and evaluated annually with a neuropsychological battery testing memory and other cognitive domains. To control for the learning effect-the improvement in test performance associated with repeated exposure-longitudinal performance was compared between two age groups. RESULTS: The older age group displayed a relative decline in memory performance with time. In contrast to memory, a relative age-related decline was not observed in tests of language, visuospatial ability, and abstract reasoning. Furthermore, within the memory domain, age-related decline was restricted to a specific aspect of memory, manifesting only in a measure sensitive to the acquisition and early retrieval of new information, and not in a measure of memory retention. This profile of age-related cognitive decline anatomically localizes to the hippocampal formation. CONCLUSION: This study establishes age-related memory decline using longitudinal data, and shows that this decline does not occur diffusely across multiple cognitive domains. Both early AD as well as non-AD processes likely contribute to age-related memory decline, and continued follow-up may reveal distinguishing features between these two.

Aged↗
PubMed1999

Differential regional dysfunction of the hippocampal formation among elderly with memory decline and Alzheimer's disease.

The hippocampal formation is composed of separate anatomical regions interconnected to form a circuit, and investigating abnormal hippocampal function is most revealing at the level of these regions. Until recently, regional analysis of the hippocampal formation could be performed only in animals or in human postmortem tissue. Here, we report a method using functional magnetic resonance imaging that evaluates the hippocampal regions in vivo, and we use this method to study elderly with normal memory, with isolated memory decline, and with probable Alzheimer's disease (AD). Although age-related memory decline occurs commonly, the cause of this decline remains unknown, with disagreement as to whether this decline represents one or more etiologies. Analysis revealed two distinct patterns of regional dysfunction among elderly with isolated memory decline--one pattern similar to that found in elders with AD, involving all hippocampal regions, and a second pattern with dysfunction restricted to only one hippocampal region, the subiculum. These results offer direct evidence of hippocampal dysfunction associated with memory decline in the elderly, and implicate both predementia AD and non-AD processes as possible underlying causes.

Aged↗
PubMed1999

Effect of literacy on neuropsychological test performance in nondemented, education-matched elders.

The current investigation compared neuropsychological test performance among nondemented literate and illiterate elders. The sample included participants in an epidemiological study of normal aging and dementia in the Northern Manhattan community. All participants were diagnosed as nondemented by a neurologist, and did not have history of Parkinson's disease, stroke, or head injury. Literacy level was determined by self-report. MANOVAs revealed a significant overall effect for literacy status (literate vs. illiterate) on neuropsychological test performance when groups were matched on years of education. The overall effect of literacy status remained significant after restricting the analyses to elders with no formal education, and after controlling for the effects of language of test administration. Specifically, illiterates obtained lower scores on measures of naming, comprehension, verbal abstraction, orientation, and figure matching and recognition. However tests of verbal list delayed recall, nonverbal abstraction, and category fluency were unaffected by literacy status, suggesting that these measures can be used to accurately detect cognitive decline among illiterate elders in this sample. Differences in organization of visuospatial information, lack of previous exposure to stimuli, and difficulties with interpretation of the logical functions of language are possible factors that contribute to our findings.

Aged↗
PubMed1998

Cognitive test performance among nondemented elderly African Americans and whites.

We examined the neuropsychological test performance of a randomly selected community sample of English-speaking non-Hispanic African American and white elders in northern Manhattan. All participants were diagnosed as nondemented by a neurologist, whose assessment was made independent of neuropsychological test scores. African American elders obtained significantly lower scores on measures of verbal and nonverbal learning and memory, abstract reasoning, language, and visuospatial skill than whites. After using a stratified random sampling technique to match groups on years of education, many of the discrepancies became nonsignificant; however, significant ethnic group differences on measures of figure memory, verbal abstraction, category fluency, and visuospatial skill remained. Discrepancies in test performance of education-matched African Americans and whites could not be accounted for by occupational attainment or history of medical conditions such as hypertension and diabetes. These findings emphasize the importance of using culturally appropriate norms when evaluating ethnically diverse elderly for dementia.

Aged↗
PubMed1996

Multiple implants for first molar prosthodontics.

Problems that can occur when single implants are utilized to restore first molar teeth include the frequent loosening of screws, as well as screws and/or implant breakage. These may result from torquing and rotational movements of the prosthesis during masticatory and parafunctional mandibular movements. When sufficient bone and mesio-distal restorative space is present, the placement of two implants should be considered.

Dental Abutments↗
PubMed1996

Sinus-lift graft: using the maxillary sinuses to support implants.

Often, the posterior region of the maxilla lacks the alveolar bone necessary to maintain an implant-supported prosthesis. The authors outline a procedure to augment the maxillary ridge using a composite alloplastic bone graft. The procedure also enables the practitioner to place implants at the time of the graft, reducing the surgical and healing time for the patient. Within six to 12 months of the bone graft, the patient can wear a fixed, implant-supported prosthesis. The authors report that patients who have been treated with this procedure have maintained stable implant prostheses for over five years.

Adult↗
PubMed1994

Provisional and definitive prostheses following sinus lift and augmentation procedures.

Sinus lift and augmentation procedures with simultaneous insertion of cylindrical root form implants can be used to treat the atrophic posterior maxilla. The long-term use of a second stage provisional prosthesis is emphasized. The recommended metal-reinforced acrylic resin provisional restoration allows treatment and/or removal of a failing implant and progressive loading before fabrication of the definitive prosthesis. Modifications in prosthesis fabrication after sinus lift surgery and augmentation procedures are discussed.

Bicuspid↗
PubMed1993

Nitric oxide and carbon monoxide produce activity-dependent long-term synaptic enhancement in hippocampus.

Nitric oxide (NO) and carbon monoxide (CO) may act as retrograde messages for long-term potentiation (LTP) in the hippocampus. Zinc protoporphyrin IX, an inhibitor of the enzyme that produces CO, blocked induction of LTP in the CA1 region of hippocampal slices. Application of either NO or CO to slices produced a rapid and long-lasting increase in the size of evoked synaptic potentials if, and only if, the application occurred at the same time as weak tetanic stimulation. This long-term enhancement was spatially restricted to synapses from active presynaptic fibers and appeared to involve mechanisms utilized by LTP, occluding the subsequent induction of LTP by strong tetanic stimulation. The enhancement by NO and CO was not blocked by an N-methyl-D-aspartate (NMDA) receptor blocker, suggesting that NO and CO act downstream from the NMDA receptor. Also, CO produced long-term enhancement when paired with low-frequency stimulation. These results are consistent with the hypothesis that NO and CO, either alone or in combination, serve as retrograde messages that produce activity-dependent presynaptic enhancement during LTP.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1993

First-stage fixed provisional restorations for implant prosthodontics.

Combination metal-and-acrylic-resin fixed provisional prostheses can be used in implant dentistry as an alternative to a removable provisional prosthesis. They may be fabricated in the laboratory and inserted on the day of fixture placement to ensure that the patients may return to their normal lifestyles with minimal discomfort or interruption in function and esthetics. These interim restorations may be used in free-standing as well as hybrid types of implant supported prostheses. The materials used and techniques of fabrication are described.

Dental Casting Technique↗
PubMed1993

Augmenting the maxillary sinus for implants: report of 27 patients.

A method for restoring the posterior portion of the maxilla with a simultaneous composite alloplastic sinus lift graft and placement of press-fit implants is presented. Sinus grafting is needed because of minimal remaining alveolar bone. The composite graft material uses a combination of demineralized freeze-dried cortical bone and Interpore 200 hydroxyapatite. Since 1987, 45 sinus grafts with simultaneous placement of 111 root-form implants have been performed for 27 patients. None of the 76 restored implants have been lost. Complications were encountered in 2 patients (4 sinuses) who were heavy smokers. Antibiotics were administered, symptoms subsided, and the implants integrated.

Adult↗
PubMed1992

Identified FMRFamide-immunoreactive neuron LPL16 in the left pleural ganglion of Aplysia produces presynaptic inhibition of siphon sensory neurons.

The gill- and siphon-withdrawal reflex of Aplysia undergoes transient inhibition following noxious stimuli such as tail shock. This behavioral inhibition appears to be due in part to transient presynaptic inhibition of the siphon sensory cells, which can be mimicked by application of the peptide FMRFamide. Although FMRFamide is widespread in the Aplysia nervous system, an FMRFamide-containing inhibitory neuron has not previously been identified. We have searched for such a neuron by combining FMRFamide immunofluorescence with fluorescent dye backfilling from the abdominal ganglion, the location of the siphon sensory cells. These methods localized a neuron in the left pleural ganglion, which we have named LPL16. LPL16 is FMRFamide immunoreactive; it is excited by tail shock; and stimulation of LPL16 produces inhibition of siphon sensory cell-to-motor cell postsynaptic potentials and narrowing of action potentials in the sensory cells in tetraethylammonium solution. These results indicate that LPL16 participates in the inhibitory effects of tail shock, and support the idea that FMRFamide plays a physiological role in the inhibition.

Animals↗
PubMed1990

Vascular reactivity of the coronary artery in rainbow trout (Oncorhynchus mykiss).

Vascular reactivity of the large coronary artery of a lower vertebrate was investigated for the first time in this study. The responses of vascular rings to various pharmacological agents were measured using isometric force transducers. Coronary arteries from rainbow trout, Oncorhynchus mykiss, contracted with acetylcholine and predominantly relaxed with isoproterenol, epinephrine, norepinephrine, and serotonin. Atenolol blocked the adrenergic relaxation, suggesting a predominance of beta 1-adrenoceptors. Nitroglycerin and sodium nitroprusside relaxed vascular rings. Responses to histamine and bradykinin were absent in this tissue. Adenosine, ADP, and ATP caused contractions that could be blocked by theophylline. The difference in vascular reactivity between that typically found in mammalian coronary arteries and that reported here for rainbow trout are discussed.

Animals↗
PubMed1989

Activity-dependent enhancement of presynaptic inhibition in Aplysia sensory neurons.

Tail shock produces transient presynaptic inhibition and longer lasting presynaptic facilitation of the siphon sensory neurons in Aplysia. The facilitation undergoes activity-dependent enhancement that is thought to contribute to classical conditioning of the gill- and siphon-withdrawal reflex. Inhibition of the sensory neurons has now also been shown to undergo activity-dependent enhancement when action potential activity in the sensory neurons is paired with inhibitory transmitter. This effect appears to involve an amplification of the same cellular mechanisms that are involved in normal presynaptic inhibition. These results suggest that activity-dependent enhancement may be a general type of associative cellular mechanism.

Action Potentials↗
PubMed1989

Surgical stents and major oral maxillofacial surgery.

The surgical guide stent constructed of acrylic is frequently of great value to help with the placement and stabilization of grafts and accurate insertion of transosteal and endosteal implants. It is the area in which the restorative dentist, dental technician, and surgeon interface.

Alveolar Ridge Augmentation↗
PubMed1989

Presurgical prosthetics and surgical templates.

An overview has been presented of the prosthodontic procedures used prior to the first stage of implant surgery, the procedures used between the first and second stages of surgery, and the prosthetic appliances fabricated prior to insertion of the definitive implant prosthesis. In addition, the need for suggestions to the surgeon for optimal implant fixture placement using surgical templates has been discussed. The design and fabrication of a preferred mandibular surgical template has been presented. In addition, it has been recommended that the surgeon and restorative dentist should employ a team approach to implantology for the best results.

Dental Implantation, Endosseous↗
PubMed1987

Tail shock produces inhibition as well as sensitization of the siphon-withdrawal reflex of Aplysia: possible behavioral role for presynaptic inhibition mediated by the peptide Phe-Met-Arg-Phe-NH2.

Recent studies have shown that, in addition to being modulated by presynaptic facilitation, the sensory neurons of the gill- and siphon-withdrawal reflex of Aplysia are also capable of being modulated by transient presynaptic inhibition produced by the peptide Phe-Met-Arg-Phe-NH2. These two modulatory effects involve different second-messenger systems: the facilitation is mediated through cAMP-dependent protein phosphorylation, and the inhibition is mediated through the lipoxygenase pathway of arachidonic acid. To explore the behavioral function of this inhibition, we have carried out a parametric analysis of the effect of tail shock on the siphon-withdrawal reflex. In addition to producing sensitization of the withdrawal reflex, tail shock also transiently inhibits the reflex. The inhibition is produced by relatively weak shock, whereas sensitization is more prominent and may mask the inhibition with stronger shock. Furthermore, inhibition is not observed after habituation training. Cellular studies suggest that the behavioral inhibition is mediated, at least in part, by presynaptic inhibition of transmitter release from the siphon sensory neurons. Moreover, we have identified an interneuron within the left pleural ganglion (LPL16) that shows Phe-Met-Arg-Phe-NH2 immunoreactivity, is activated by tail shock, and simulates the presynaptic inhibitory actions produced by tail shock. Therefore, our results suggest that presynaptic inhibition mediated by Phe-Met-Arg-Phe-NH2 and its lipoxygenase second messenger contributes to behavioral inhibition of the siphon-withdrawal reflex.

Action Potentials↗