Biomedical subjects

C Hock

Publications and source records attributed to C Hock.

4 recordsLinked to original sources

PubMed1992

Nerve growth factor and choline acetyltransferase activity levels in the rat brain following experimental impairment of cerebral glucose and energy metabolism.

Intracerebroventricular (ICV) injection of streptozotocin (STZ) has been reported to impair cerebral glucose utilization and energy metabolism (Nitsch and Hoyer: Neurosci Lett, 128:199-202, 1991) and also to prejudice passive avoidance learning in adult rats (Mayer et al.: Brain Res 532:95-100, 1990). It is well established that the forebrain cholinergic system, whose integrity is essential for learning and memory functions, depends on the target-derived retrograde messenger nerve growth factor (NGF). Therefore, we measured NGF and choline acetyltransferase (ChAT) activity levels in the forebrain cholinergic system in adult rats that had received a single injection of either STZ or artificial cerebrospinal fluid into the left ventricle 1 or 3 weeks prior to sacrifice. One week after ICV STZ treatment, NGF content was significantly decreased (-32%) in the septal region, where NGF-responsive cell bodies are located and NGF exerts its neurotrophic action after retrograde transport from NGF-producing targets. In contrast, NGF levels in the cortex and hippocampus, which are target regions for the basal forebrain cholinergic neurons, and in the brainstem and cerebellum were increased (+12% to +47%) within 3 weeks after ICV STZ treatment. The alterations in NGF levels were not related to changes in ChAT activity that decreased in the hippocampus by only 15%. This might be due to masking effects exerted by compensatory NGF-mediated stimulation of ChAT activity in remaining functional neurons. It is suggested that impaired behavior which has been observed after STZ-induced impairment of cerebral glucose and energy metabolism may be at least partially related to a diminished capacity of central NGF-responsive neurons to bind and/or transport NGF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Diabetes mellitus-associated decrease in nerve growth factor levels is reversed by allogeneic pancreatic islet transplantation.

After an untreated 5-month duration of streptozotocin (STZ)-induced diabetes mellitus (DM), nerve growth factor (NGF) levels in BDE rats were decreased to 45-65% of control in the sympathetically innervated target organs iris and submandibular gland, in the superior cervical ganglion (containing NGF-dependent sympathetic perikarya projecting to the cranial targets), and in the NGF-transporting sciatic nerve. Successful allogeneic pancreatic islet transplantation (providing a physiological glucose homeostasis without immunosuppression) after 3-4 weeks of DM reversed the DM-related decrease in NGF levels 4 months after transplantation as compared with untreated diabetic rats. By contrast, NGF levels in the treated vas deferens (innervated by short postganglionic sympathetic neurons) remained increased as in the untreated diabetic rats (175% of control). Thus, DM-associated changes in endogenous NGF levels seem to be reversible by institution of metabolic control, at least at an early stage of DM when NGF-responsive neurons have not been deprived of NGF for a long time.

Animals↗

PubMed1990

Nerve growth factor levels and choline acetyltransferase activity in the brain of aged rats with spatial memory impairments.

Nerve growth factor (NGF) and choline acetyltransferase (ChAT) activity levels were measured in 7 different brain regions in young (3-month-old) and aged (2-years-old) female Sprague-Dawley rats. Prior to analysis the spatial learning ability of the aged rats was assessed in the Morris' water maze test. In the aged rats a significant, 15-30%, increase in NGF levels was observed in 4 regions (septum, cortex, olfactory bulb and cerebellum), whereas the levels in hippocampus, striatum and the brainstem were similar to those of the young rats. The NGF changes did not correlate with the behavioral performance within the aged group. Minor 15-30%, changes in ChAT activity were observed in striatum, brainstem and cerebellum, but these changes did not correlate with the changes in NGF levels in any region. The results indicate that brain NGF levels are maintained at normal or supranormal levels in rats with severe learning and memory impairments. The results, therefore, do not support the view that the marked atrophy and cell loss in the forebrain cholinergic system that is known to occur in the behaviorally impaired aged rats is caused by a reduced availability of NGF in the cholinergic target areas. The results also indicate that the slightly increased levels of NGF are not sufficient to prevent the age-dependent atrophy of cholinergic neurons, although they might be important for the stimulation of compensatory functional changes in a situation where the system is undergoing progressive degeneration.

Aging↗

PubMedDate not supplied

The technique of obtaining pancreatic segments in dogs: surgical-anatomical aspects.

The technique of obtaining pancreatic segments was studied in 60 mongrel dogs by removing the right pancreatic lobe. At the same time comparative surgical-anatomical examinations were performed for the detection of the vascular variations of the right pancreatic segment. In 83% of the cases the arterious and venous systems were suitable for gaining grafts (Types I-II). In 12% the segment was suitable for grafting only if the venous network had an optimal course (Type III), while in 5% the segment was unsuitable because it did not have a suturable arterial stump (Type IV).

Animals↗