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Biomedical subjects

K Grant

Publications and source records attributed to K Grant.

At least 73 records · Page 4Linked to original sources
PubMed1989

Effect of thermal injury in the rat on transfer of IgA protein into bile.

Severe thermal injury is associated with bacterial sepsis; the intestine is considered a likely source of invasive organisms. Because IgA antibody in bile accounts for much of the specific immune defense of the upper intestinal tract in the rat, the effect of thermal injury on the quantity of IgA protein in bile was examined. Sprague-Dawley rats received a 20% to 30% body surface area burn under anesthesia. Eighteen hours later the common bile duct was cannulated and bile was collected for three hours. Total IgA protein in bile decreased 90% after thermal injury. The bile volume, the concentration of bile protein, and free secretory component did not change significantly. Although blood flow to the liver 18 hours after thermal injury was not changed, there was a significant reduction in total IgA concentration in the circulation; both monomeric (m-IgA) and polymeric IgA (p-IgA) were decreased. This finding may explain, in part, the reduced concentration of IgA protein in bile. Although not examined in this study, decreased local hepatic synthesis and/or transport of p-IgA across the hepatocyte may also contribute to the reduced IgA levels in bile.

Animals↗
PubMed1989

Ultrastructural and histochemical investigations of Call-Exner bodies in rabbit Graafian follicles.

In a histological survey of 19 mammalian species, Call-Exner bodies of conventional size and appearance were found in only 5, namely, human, rhesus monkey, rabbit, guinea-pig and sheep. Rabbit ovaries were used for characterizing these bodies using quantitative histochemistry, lectin binding and electron microscopy. Call-Exner bodies were topographically distinct lacunae of the extracellular space probably containing hyaluronic acid with proteoglycan complexes. The staining characteristics of the antrum and Call-Exner bodies were generally similar. However, in contrast to the antrum, the smaller lacunae contained suspended filaments with a distinctive peripheral membrane upon which a rosette of granulosa cells was resting. The membrane and narrow intercellular clefts probably prevent much exchange of large glycosaminoglycan complexes with the antrum. The origin and significance of Call-Exner bodies require further study, but it is clear that they are associated with secretion rather than with necrosis as sometimes suggested.

Animals↗
PubMed1989

Health-care decision making, Part II. Choices for incapacitated patients.

The traditional, informal approach to making medical decisions for incapacitated patients is often inappropriate today. Guidelines are needed in two major areas: assessing incapacity and seeking surrogate decision makers. Judicially declared incompetency does not necessarily imply incapacity to make medical choices. Proposed standards for determining incapacity require a multistep evaluation of the patient's abilities to understand, reason, and communicate. When decisions must be made for an incapacitated patient, priority is given to the patient's previously stated preferences. An advance directive--living will or durable power of attorney--simplifies the process. If no advance directive was prepared, a surrogate decision maker may be designated according to applicable state statutes. Standards are still evolving for protecting the autonomy and best interests of vulnerable, incapacitated patients.

Decision Making↗
PubMed1989

Health-care decision making. Part I: Legal and ethical principles.

The growing elderly population and the acquired immunodeficiency syndrome (AIDS) epidemic have focused attention on ethical and legal issues surrounding health-care decision making. It is becoming increasingly critical to involve patients in the decisions that affect their care. Legal frameworks are evolving to protect the rights of both "competent" and "incompetent" patients. By writing instructions in advance, patients can increase their control and autonomy over health-care decisions. Physician assistants can facilitate the process by incorporating a patient value history into the chart and explaining legally recognized documents. Living wills generally apply in the context of terminal illness or irreversible coma; however, definitions of terminal conditions, imminent death, or life-sustaining procedures can be problematic. A number of states recognize the health-care durable power of attorney, which establishes a surrogate decision maker to act with specific instructions and limitations should the patient become incompetent or incapacitated.

Decision Making↗
PubMed1989

Humoral immune responses to XMMCO-791-RTA immunotoxin in colorectal cancer patients.

Monoclonal antibody 791 (XMMCO-791) recognizes a colorectal tumour-associated antigen. Antibody 791-ricin A chain immunotoxin (XMMCO-791-RTA) inhibits growth of human tumour xenografts and it is therefore being evaluated for the treatment of colorectal cancer. One of the problems with therapy with mouse monoclonal antibodies is they stimulate humoral responses in patients. However antigens linked to ricin are cytotoxic for B cells and therefore XMMCO-791-RTA may not be immunogenic. The humoral antibody response to murine monoclonal antibody XMMCO-791 (IgG2b) conjugated to the plant toxin, ricin A chain (RTA), was measured in colorectal cancer patients in a phase I clinical trial. All patients produced strong responses to the XMMCO-791 immunoglobulin and to RTA. The predominant response to the antibody was against the idiotypic determinant although anti-subclass and anti-mouse antibodies were also detected. A component of the anti-idiotypic immunoglobulin response in the colorectal cancer patients was directed against the combining site of XMMCO-791. These antibodies inhibited in-vitro binding of XMMCO-791 to target 791 cells and so may be inhibitors of repeated immunotoxin therapy. Immunotoxins do not abrogate the immune response to mouse immunoglobulin in vivo but instead are highly immunogenic.

Adult↗
PubMed1989

Corollary discharge inhibition and preservation of temporal information in a sensory nucleus of mormyrid electric fish.

Knollenorgan electroreceptors in mormyrid fish are concerned with electrocommunication, i.e., with detecting electric organ discharges (EODs) of other electric fish. But knollenorgan electroreceptors are also activated by the fish's own EOD. Potential interference by such self-stimulation is blocked by an inhibitory corollary discharge in the nucleus of the electrosensory lateral line lobe (NELL), the first central relay of the knollenorgan pathway. This study used intracellular recording and staining to examine the mechanism of the corollary inhibition and the specializations in anatomy and physiology that permit the accurate relaying of temporal information about the EODs of other fish. Several events are recorded inside primary knollenorgan afferents in addition to a large orthodromic action potential. The additional events include small orthodromic electronic epsps, postsynaptic action potentials, and a corollary discharge inhibitory postsynaptic potential (ipsp) associated with the EOD motor command. These additional events are also recorded in NELL cells and almost certainly originate there. Electrical coupling between afferents and cells makes it possible to observe the events inside primary afferents. The corollary discharge ipsp in the cell is associated with a conductance increase and inverts rapidly when recorded with chloride-containing electrodes, supporting a hypothesis of GABA mediation. The ipsp lasts longer in cells than in afferents. Each electrotonic excitatory postsynaptic potential (epsp) is probably caused by a single primary afferent, and any one of several epsps in a given cell seems capable of eliciting a postsynaptic spike in that cell. The epsps follow stimulation rates as high as 500/sec with minimal variability. No lateral inhibition is observed in NELL. These and other properties indicate that the knollenorgan pathway is specialized for temporal information rather than spatial or intensity information.

Action Potentials↗
PubMed1987

Convergence of electrotonic club endings, GABA- and serotoninergic terminals on second order neurons of the electrosensory pathway in mormyrid fish, Gnathonemus petersii and Brienomyrus niger (Teleostei).

Previous electrophysiological data indicate that the afferent electrosensory impulses conveyed towards the mesencephalon are blocked in the rhombencephalic electrosensory lateral line nucleus (nELL) by the concomitantly occurring EOD (electric organ discharge) command-associated (corollary) discharge. Electron-microscopic observations and anterograde labeling with horseradish peroxidase show that the primary electrosensory fibers terminate with club endings on the adendritic soma of the nELL cells and form gap junctions with the postsynaptic membrane. The remaining part of the soma and the initial segment membrane of nELL cells are covered with a large number of boutons showing chemical synaptic profiles. The GABA-ergic (gamma-aminobutyric-acid) nature of the majority of the boutons is revealed immunocytochemically by anti-GABA and anti-glutamic acid decarboxylase (anti-GAD) antisera, as seen in the light microscope. Electron-microscopic examination confirms the GABAergic nature of most of the bouton-like terminals, whereas club endings show negative immunoreactivity. In addition, serotonin-immunoreactive fibers and boutons are found in the same nucleus, between and next to the nELL cells. It is suggested that the GABAergic endings are the morphological basis for the inhibition that occurs in the nELL and that is mediated by the corollary discharge.

Animals↗
PubMed1986

Morphology and physiology of the brainstem nuclei controlling the electric organ discharge in mormyrid fish.

The motoneurons to the mormyrid electric organ are driven from the medullary relay nucleus. This nucleus is in turn innervated by an adjacent cell group, nucleus C. The goals of this study were to characterize the morphology and physiology of neurons in these two nuclei, and to test the hypothesis that nucleus C is the command nucleus responsible for initiating the electric organ discharge. Medullary relay neurons and nucleus C neurons were recorded intracellularly and labeled with horseradish peroxidase. Medullary relay neurons have a richly branched dendritic arborization, confined mainly to the nucleus itself, and somatosomatic, dendrosomatic, and presynaptic dendro-axonal gap junctions have been observed. Medullary relay neuron axons descend to the spinal cord without branching. Nucleus C dendrites extend far into the ventral reticular formation. Axons of nucleus C neurons have one branch that ramifies densely within the medullary relay nucleus, forming large club endings on the medullary relay neuron soma. Two additional branches project bilaterally toward the bulbar command associated nuclei. Both medullary relay neurons and nucleus C neurons fire a double action potential that precedes each electric organ discharge. Activity in nucleus C precedes that in the medullary relay nucleus by 100-300 microseconds. Postsynaptic activity is recorded in nucleus C neurons but not in medullary relay neurons. Hyperpolarization of a single nucleus C neuron can lower the frequency of the electric organ discharge. Both morphological and physiological data indicate that nucleus C is an integrating center where the electric organ command is initiated.

Action Potentials↗
PubMed1986

Blunt rupture of both atrioventricular valves.

Younger patients are surviving extensive damage to the heart and supporting structures, often associated with multiple systems injuries. A 23-year-old patient who sustained blunt trauma to the chest resulting in a pericardial laceration, injury to tricuspid and mitral valves, myocardial contusion, and paresis of the left phrenic nerve is reported. Porcine bioprosthetic valve replacement of both atrioventricular valves was necessary. Prompt diagnosis and aggressive intervention of such injuries can lead to successful repair of complex cardiac trauma.

Adult↗
PubMed1986

Red nucleus inputs to retractor bulbi motoneurones in the cat.

Rubral projections to retractor bulbi motoneurones were investigated by intracellular recording in the accessory abducens nucleus in the cat. Their post-synaptic effects were compared with those of trigeminal afferent pathways. Post-synaptic potentials evoked by stimulation of the contralateral red nucleus were predominantly excitatory, with latencies in the monosynaptic range. Post-synaptic potentials evoked by stimulation of the ipsilateral red nucleus, at threshold, were predominantly inhibitory with latencies indicating a di- or trisynaptic pathway. At above threshold intensity, an earlier excitatory post-synaptic potential (e.p.s.p.) preceded the inhibitory post-synaptic potential (i.p.s.p.) in about half the recorded neurones. Convergence of rubral and trigeminal inputs was also observed in other neurones, not identified as retractor bulbi motoneurones, but situated within the accessory abducens nucleus.

Abducens Nerve↗
PubMed1986

Organization of synaptic transmission in the mammalian solitary complex, studied in vitro.

1. Synaptic transmission and neuronal morphology were studied in the nucleus tractus solitarius and in the dorsal vagal motor nucleus (solitary complex), in coronal brain-stem slices of rat or cat, superfused in vitro. 2. Electrical stimulation of afferent fibres of the solitary tract evoked two different types of post-synaptic response recorded intracellularly in different solitary complex neurones. Labelling with horseradish peroxidase showed that these two sorts of orthodromically evoked responses were correlated with different post-synaptic neuronal morphologies. 3. The majority of recorded neurones (n = 93) showed a prolonged reduction in excitability following the initial solitary-tract-evoked excitatory post-synaptic potential (e.p.s.p.). A smaller number of neurones (n = 53) showed a prolonged increase in excitability following solitary tract stimulation. In no case did the solitary tract stimulation induce a burst of action potentials at high frequency. 4. The time-to-peak and the half-width of the initial solitary-tract-evoked e.p.s.p. were shorter in neurones with prolonged increased excitability than in those with prolonged reduced excitability. In neurones with prolonged reduced excitability, this e.p.s.p. was followed by a hyperpolarization lasting 60-100 ms. The latency of this inhibitory post-synaptic potential (i.p.s.p.) was 3-5 ms longer than that of the initial e.p.s.p. and its reversal potential was 10 mV more negative than the reversal potential of the response measured following application of gamma-aminobutyric acid or glycine. In neurones with prolonged increased excitability, at a membrane potential of -40 to -50 mV, the initial solitary tract e.p.s.p. was followed by a prolonged depolarization lasting 100-400 ms. 5. Background synaptic activity was high in neurones with prolonged increased excitability, consisting of unitary e.p.s.p.s with an amplitude of more than 0.8 mV. This activity was increased for a period of 300-800 ms following solitary tract stimulation. Spontaneous excitatory potentials of more than 0.5 mV were not seen in neurones with prolonged reduced excitability. In these neurones, after intracellular injection of choride ions, reversed unitary i.p.s.p.s formed a background activity which was increased following stimulation of the solitary tract. 6. Neurones with prolonged reduced excitability were found in the medial, ventral and ventrolateral part of the nucleus tractus solitarius and in the dorsal vagal motor nucleus where they were identified by their antidromic response to stimulation ventral and lateral to the tractus solitarius.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1986

Traumatic aortic insufficiency after blunt chest trauma.

Traumatic aortic insufficiency is an uncommon result of blunt trauma. The typical clinical features include trauma, followed by pain (and often syncope), a musical aortic diastolic murmur, and progressive cardiac decompensation. Shock is an unusual manifestation of traumatic aortic insufficiency. In this report, a patient is described who experienced shock, a widened mediastinum, and failure to respond to fluid resuscitation after cardiac injury in an automobile accident. Emergency surgery was performed and an intimal tear was repaired. A #25 Carpentier-Edwards bioprosthesis was used to replace the aortic valve, which was avulsed from the commissure of the right and left cusps. Since aortic valve replacement offers an excellent prognosis, it should be done at the first signs of cardiac decompensation.

Journal Article↗
PubMed1986

Global stereopsis in stroke patients.

Contradictory evidence has been presented in the literature on the existence of a right-hemisphere mechanism subserving global stereopsis. In the present study evoked responses to dynamic random-dot stereograms were recorded from International 10-20 scalp sites O2, P4, T6, T4 and homotopic sites over the left hemisphere. Stroke patients with unilateral lesions were selected on the basis of satisfactory performance on ocular screening tests and on clinical or objective indications that dementia was absent. Control subjects were found among the relatives of patients. The stereopsis test schedule included left, right and centre field presentations of 30 arc min, disparities. The dot density of the disparity, relative to that of the remainder of the random dot field, was manipulated to provide a full contrast stimulus and a no-contrast uniform field stimulus, thus varying the availability of monocular cues provided by the contrast factor. Latency and amplitude of the evoked potentials were computed and submitted to analyses of variance. No significant results were found which supported the proposition of a lateralized mechanism for global stereopsis. This conclusion is in conflict with the findings of some earlier reports. It is suggested that the techniques used in the earlier experiments may not have been adequate for the study of the questions involved.

Aged↗
PubMed1986

The use of the computer in the dermatopathology laboratory.

On a regular basis we are upgrading and modifying our software package to meet our ever-changing needs. The day of the user-friendly computer is upon us. We have found the computer to be an ever-important extension of our own minds, truly our own electronic servant. It has relieved us of the mental tedium that in the past has eaten up so much of our time, leaving us free to accomplish the tasks that our electronic servant could never accomplish, including the creation of new ideas and the appreciation and nurturing of old ones.

Accounting↗